diff --git a/B09_Estimation/B09_Estimation_Labor_Source.py b/B09_Estimation/B09_Estimation_Labor_Source.py
index 5d0f43c11..621602eee 100644
--- a/B09_Estimation/B09_Estimation_Labor_Source.py
+++ b/B09_Estimation/B09_Estimation_Labor_Source.py
@@ -289,10 +289,13 @@ class Builder:
                 if bid is None:
                     why = "단가산출을 못 셈(바탕 없음 · 순환)"
                     return {"kind": "blank", "name": name, "qty": each, "why": why}
-                from M02_MasterTemplete.M02_Sangeun_Calc import times_of
+                from M02_MasterTemplete import M02_Sangeun_Calc as sc
 
                 block = self.blocks[bid]  # 블록 = 굳힌 줄 결과단위(배) 몫 · M02 참조 줄 = 1 단위
-                per = float(times_of(whole.logic(doc["바탕"]["로직"])))
+                try:  # 배 = 바탕 기준단위 → SK 단위(728-2)
+                    per = float(sc.ratio_of(doc, whole.logic(doc["바탕"]["로직"]), whole))
+                except sc.sd.DocError as e:
+                    return {"kind": "blank", "name": name, "qty": each, "why": str(e)}
                 return {"kind": "daega", "key": bid, "name": block["name"], "unit": block["unit"],
                         "qty": None if each is None else each / per}  # fmt: skip
             if refs.kind_of(ref.get("키")) == "promote":  # 옛 단가승격 참조 = 일위대가화 = 대가
diff --git a/M02_MasterTemplete/M02_MasterTemplete_Find_Pick.ts b/M02_MasterTemplete/M02_MasterTemplete_Find_Pick.ts
index ec5c7764a..a1f8ae0cc 100644
--- a/M02_MasterTemplete/M02_MasterTemplete_Find_Pick.ts
+++ b/M02_MasterTemplete/M02_MasterTemplete_Find_Pick.ts
@@ -10,6 +10,7 @@
  *  · 부르는 곳 = M02 단가산출 [항목 추가](`Sangeun_Pick`) · 일위대가 [로직 추가]
  *    (`Labor_Pick` 이 `lib.sangeun` 이면 이 창) — B09 · 불러오기는 옛 창(`Labor_Pick`)
  *  · (727-1) 기초 = 로직마다 한 줄(`logicHeads` · 옵션은 넣은 뒤 고름 · 옛 창도 같이) · 서버 목록 그대로
+ *  · (728-2) 돈 아닌 기초(결과단위가 「원」 아님 · ㎥/시간 등 21 개) = 목록에서 뺌
  * ========================================================================== */
 
 import { createDataTable } from "@ui/ui_template_data_table";
@@ -153,6 +154,7 @@ export function openFindPicker(opt: FindPickOptions): void {
       const hit = matchLogic(q, { ...x, 이름: `${x.이름} ${x.규격}` }); // 공용 · 208-1
       if (!hit.ok) return [];
       const logic = logics.find((y) => y.키 === x.키);
+      if (logic && !logic.결과단위.trim().startsWith("원")) return []; // 돈 아닌 기초(작업량 · 728-2) 뺌
       return [
         {
           품명: join(x.이름, aliasNote(hit.alias)),
diff --git a/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Detail.ts b/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Detail.ts
index 9117b578f..6262c473e 100644
--- a/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Detail.ts
+++ b/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Detail.ts
@@ -20,6 +20,7 @@ import { createInputField } from "@ui/ui_template_input";
 import { t as L } from "@ui/ui_template_locale";
 import { createText } from "@ui/ui_template_text";
 import { calcSheetRows } from "../A00_Common/calc_sheet";
+import { swapUnit } from "../A00_Common/master_unit_swap";
 import { buildCalc } from "../M01_MasterData/M01_MasterData_UI_Logic_Calc";
 import {
   fetchLogic,
@@ -37,6 +38,7 @@ import { createViewPicker } from "../M01_MasterData/M01_MasterData_UI_LogicLab_V
 import type { Layer } from "./M02_MasterTemplete_Api_Fetch";
 import { calcSangeun, removedStrip } from "./M02_MasterTemplete_Sangeun_Cover";
 import { openSangeunLinePicker } from "./M02_MasterTemplete_Sangeun_Pick";
+import { baseUnitOf, buildUnitSwap, type SwapHow } from "./M02_MasterTemplete_Sangeun_Unit";
 import {
   baseCovers,
   dropBase,
@@ -65,8 +67,6 @@ export interface SangeunDetailOptions {
 
 const LIB = { read: "/m02/logic-lib", calc: "/m02/logic-lib" };
 const clone = <T>(v: T): T => JSON.parse(JSON.stringify(v)) as T;
-/** 결과단위 「원/10㎡」 → SK 단위 「㎡」(1 단위 값 · 배는 서버가 나눔) */
-const unitOf = (result: string): string => result.replace(/^원\s*\/\s*[\d.,]*\s*/, "").trim();
 
 export function mountSangeunDetail(
   host: HTMLElement,
@@ -105,6 +105,7 @@ export function mountSangeunDetail(
     onClick: () =>
       openSangeunLinePicker(scope, (line) => {
         if ("종류" in line && line.종류 === "로직" && !doc.바탕) return setBase(line.로직);
+        if ("종류" in line && line.종류 === "로직") return void addBase(line);
         doc.더한줄 = [
           ...(doc.더한줄 ?? []),
           line as unknown as NonNullable<SkDoc["더한줄"]>[number],
@@ -113,6 +114,25 @@ export function mountSangeunDetail(
       }),
   });
   addButton.hidden = !edit;
+  /** 둘째 기초(728-2) — 수량 처음값 = 바탕 기준단위 1 개 = 그 기초 기준단위 몇 개(같은 성격 · 다르면 1) */
+  async function addBase(line: { 로직: string; 수량: number }): Promise<void> {
+    let qty = 1;
+    const have = base ? baseUnitOf(base.logic.결과단위) : "";
+    try {
+      const swap = have
+        ? swapUnit(have, baseUnitOf((await fetchLogic(line.로직)).logic.결과단위))
+        : null;
+      if (swap?.배 != null && swap.계수 === null) qty = swap.배;
+    } catch {
+      /* 못 읽음 = 1 그대로 */
+    }
+    if (!alive) return;
+    doc.더한줄 = [
+      ...(doc.더한줄 ?? []),
+      { ...line, 수량: qty } as unknown as NonNullable<SkDoc["더한줄"]>[number],
+    ];
+    touch();
+  }
   /** 첫 기초 = 바탕(옛 [기본 로직 선택] 동작 · 단위는 `loadBase` 가 기초 결과단위로) */
   function setBase(key: string): void {
     doc.바탕 = { 로직: key };
@@ -215,9 +235,23 @@ export function mountSangeunDetail(
     const baseName = base ? `${base.logic.키} ${base.logic.이름}` : null;
     const baseText = baseName ?? doc.바탕?.참조?.키 ?? L("M02_SangeunNoBase");
     const revised = revisedBase();
+    const swap = base
+      ? buildUnitSwap({
+          result: base.logic.결과단위,
+          unit: doc.단위 ?? "",
+          how: doc.환산 as SwapHow | undefined,
+          edit,
+          onChange: (how) => {
+            if (how) doc.환산 = how;
+            else delete doc.환산;
+            touch();
+          },
+        })
+      : null;
     head.replaceChildren(
       field(L("M02_Name"), "이름"),
       field(L("M02_SangeunUnit"), "단위"),
+      ...(swap ? [swap] : []),
       el("div", {
         className: "m02-sk__tags",
         attrs: { "data-sk-base": baseKey() ?? "" },
@@ -303,7 +337,7 @@ export function mountSangeunDetail(
         ? calcSheetRows({
             묶음: sheetGroups(rows),
             계: ans.기준?.계 ?? null,
-            sumLabel: `${L("M02_SangeunTotal")} (${row.결과단위 || "원"})`,
+            sumLabel: `${L("M02_SangeunTotal")} (${doc.단위 && doc.단위 !== "식" ? `원/${doc.단위}` : row.결과단위 || "원"})`,
             bundle: true,
             inputs: row.입력,
             values,
@@ -423,7 +457,7 @@ export function mountSangeunDetail(
     });
   }
 
-  /** `fresh` = 막 넣은 바탕 — 단위가 비거나 「식」이면 기초 결과단위(앞 수 뗌 · 배는 서버가 나눔) */
+  /** `fresh` = 막 넣은 바탕 — 단위가 비거나 「식」이면 기초 기준단위(「100본」 · 바꾸면 서버가 환산 · 728-2) */
   async function loadBase(fresh = false): Promise<void> {
     const key = baseKey();
     base = null;
@@ -437,7 +471,7 @@ export function mountSangeunDetail(
     }
     if (!alive) return;
     if (fresh && base && (!doc.단위 || doc.단위 === "식")) {
-      doc.단위 = unitOf(base.logic.결과단위) || doc.단위;
+      doc.단위 = baseUnitOf(base.logic.결과단위) || doc.단위;
       touch(false);
     }
     draw();
diff --git a/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Unit.ts b/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Unit.ts
new file mode 100644
index 000000000..e726ffb48
--- /dev/null
+++ b/M02_MasterTemplete/M02_MasterTemplete_Sangeun_Unit.ts
@@ -0,0 +1,103 @@
+/* =============================================================================
+ * M02_MasterTemplete_Sangeun_Unit.ts
+ * 단가산출(SK) 단위 환산 칸(PLAN 728-2 · 요구서_내역19 3장 5) — 바탕 기준단위(「100본」) → SK 단위 근거 글 ·
+ *   같은 성격 = 배 자동(글만) · 성격 다름 = 환산 계수 칸 · 부피 ↔ 무게 = 단위중량 표(CC000337) 고르기.
+ *   칸 보임 · 근거 글 = `swapUnit`(짝 `A00_Common/master_unit_swap.ts`) · 셈 = 서버(`M02_Sangeun_Calc.ratio_of`)
+ *   문서 칸 `환산` {계수 | 단위중량 {종별, 형상}}(꼴 = 서버 `M02_Sangeun_Doc._swap_how`) · 바꿈 = 캐시 → [저장].
+ * ========================================================================== */
+
+import { el } from "@ui/ui_template_elements";
+import { createInputField, createSelectField } from "@ui/ui_template_input";
+import { t as L } from "@ui/ui_template_locale";
+import { createText } from "@ui/ui_template_text";
+import { swapUnit } from "../A00_Common/master_unit_swap";
+import { loadTable } from "../M01_MasterData/M01_MasterData_UI_Logic_Note";
+
+export interface SwapHow {
+  계수?: number;
+  단위중량?: { 종별: string; 형상: string };
+}
+
+const WEIGHT_TABLE = "CC000337";
+
+/** 결과단위 「원/100본」 → 기준단위 「100본」(SK 단위 처음 값) */
+export const baseUnitOf = (result: string): string => result.replace(/^원\s*\/\s*/, "").trim();
+
+/** 단위중량 표 줄 → ㎏/㎥(위 끝 · 서버 `master_unit.unit_weight` 기본과 같음) */
+const rhoOf = (row: Record<string, unknown> | undefined): number | null =>
+  row && Number.isFinite(Number(row.위)) ? Number(row.위) : null;
+
+/** 환산 칸 — 「식」 · 빈 단위 · 바탕 없음 = null(옛 셈) */
+export function buildUnitSwap(opt: {
+  result: string;
+  unit: string;
+  how: SwapHow | undefined;
+  edit: boolean;
+  onChange: (how: SwapHow | undefined) => void;
+}): HTMLElement | null {
+  const have = baseUnitOf(opt.result);
+  if (!have || !opt.unit || opt.unit === "식") return null;
+  const how = opt.how ?? {};
+  const probe = swapUnit(have, opt.unit, 1000, how.계수);
+  const root = el("div", { className: "m02-sk__tags", attrs: { "data-sk-swap": "" } });
+  const note = createText("", "muted", 14);
+  const say = (rho: number | null): void => {
+    const got = swapUnit(have, opt.unit, rho, how.계수);
+    note.textContent = got.근거;
+    note.dataset.skSwapBlocked = got.배 === null ? "1" : "";
+  };
+  if (probe.계수 === "사용자") {
+    const [, ua] = probe.가;
+    const [, ub] = probe.나;
+    const box = createInputField({
+      label: `${L("M02_SangeunSwapCoef")} — 1 ${ua} = ? ${ub}`,
+      type: "number",
+      value: how.계수 != null ? String(how.계수) : "",
+      min: 0,
+      compact: true,
+      size: 28,
+    });
+    box.input.dataset.skSwapCoef = "";
+    box.input.disabled = !opt.edit;
+    box.input.addEventListener("change", () => {
+      const v = Number(box.input.value);
+      opt.onChange(Number.isFinite(v) && v > 0 ? { 계수: v } : undefined);
+    });
+    root.append(box.root);
+  } else if (probe.계수 === "단위중량") {
+    const pick = how.단위중량;
+    const value = pick ? `${pick.종별}|${pick.형상}` : "";
+    const select = createSelectField({
+      label: `${L("M02_SangeunSwapWeight")} (${WEIGHT_TABLE})`,
+      options: [{ value: "", text: L("M02_SangeunSwapPick") }],
+      value,
+      compact: true,
+      size: 28,
+      disabled: !opt.edit,
+      onChange: (v) => {
+        const [종별, 형상] = v.split("|");
+        opt.onChange(v ? { 단위중량: { 종별, 형상 } } : undefined);
+      },
+    });
+    select.select.dataset.skSwapWeight = "";
+    root.append(select.root);
+    void loadTable(WEIGHT_TABLE).then((table) => {
+      const rows = table?.줄 ?? [];
+      select.setOptions(
+        [
+          { value: "", text: L("M02_SangeunSwapPick") },
+          ...rows.map((r) => ({
+            value: `${String(r.종별)}|${String(r.형상)}`,
+            text: `${String(r.종별)} · ${String(r.형상)} (${String(r.위)}㎏/㎥)`,
+          })),
+        ],
+        value,
+      );
+      say(rhoOf(rows.find((r) => r.종별 === pick?.종별 && r.형상 === pick?.형상)));
+    });
+  }
+  say(null);
+  if (!root.childElementCount && !note.textContent) return null;
+  root.append(note);
+  return root;
+}
diff --git a/M02_MasterTemplete/M02_Sangeun_Calc.py b/M02_MasterTemplete/M02_Sangeun_Calc.py
index 4cc7e3534..d46b8f5c4 100644
--- a/M02_MasterTemplete/M02_Sangeun_Calc.py
+++ b/M02_MasterTemplete/M02_Sangeun_Calc.py
@@ -11,6 +11,10 @@
 (B09 굳힘도 그 값) · 화면 셈 길(`calc_doc`) = 그 줄 덧칸 `펼침`(세부 줄 × 수량) · `뺀세부` ·
 `바탕판` ·
 `꼬리표`(원문번호) · 답 `꼬리표` = 바탕 원문번호.
+SK 단위 환산(728-2) = 배 = 바탕 기준단위(「100본」) → SK 단위(`master_unit.swap` ·
+「식」 · 빈 단위 = 앞 수 뗀 바탕 단위 = 옛 셈) ·
+다른 성격 = 문서 `환산` {계수 | 단위중량 {종별, 형상}} · 없으면 셈 막음(까닭) ·
+화면 셈 길 줄 · 계 = SK 1 단위 몫(`per_unit`).
 """
 
 from __future__ import annotations
@@ -56,6 +60,39 @@ def times_of(row: dict) -> Decimal:
     return per[0][0] if len(per) == 1 else Decimal(1)
 
 
+def base_unit(row: dict) -> tuple[str, str] | None:
+    """바탕 기준단위 — 「원/100본」 → (「100본」, 「본」) · 분모 없거나 여럿 = None."""
+    from M01_MasterData import M01_MasterData_Store_Combo as combo_store
+
+    per = combo_store.mu.per(row.get("결과단위"))
+    if len(per) != 1:
+        return None
+    n, u = per[0]
+    return (u if n == 1 else f"{format(n, 'f')}{u}", u)
+
+
+def ratio_of(doc: dict, row: dict, whole: Any) -> Decimal:
+    """SK 배(728-2) — 바탕 기준단위 1 개 = SK 단위 몇 개 · 1 단위 = 기준 ÷ 배 ·
+    못 바꿈 = `DocError`."""
+    from M01_MasterData import M01_MasterData_Store_Combo as combo_store
+
+    mu = combo_store.mu
+    got = base_unit(row)
+    if got is None:
+        return Decimal(1)
+    want = str(doc.get("단위") or "").strip()
+    want = (
+        got[1] if want in ("", "식") else want
+    )  # 일위대가 줄 · 「식」 = 옛 셈(앞 수 뗀 바탕 단위)
+    how = doc.get("환산") or {}
+    pick = how.get("단위중량") or {}
+    rho = mu.unit_weight(whole, pick.get("종별"), pick.get("형상")) if pick else None
+    swap = mu.swap(got[0], want, rho, how.get("계수"))
+    if swap["배"] is None:
+        raise sd.DocError(f"단가산출 단위 · {swap['근거']}")
+    return swap["배"]
+
+
 def fingerprint(row: dict) -> str:
     raw = json.dumps(row, ensure_ascii=False, sort_keys=True, default=str)
     return hashlib.sha256(raw.encode("utf-8")).hexdigest()[:16]
@@ -113,7 +150,7 @@ def resolve(
         "짝잃음": base["짝잃음"] + got["짝잃음"],
         "입력값": {**base["입력값"], **(doc.get("입력값") or {})},
         "켜쌓기율": rate,
-        "배": times_of(base["줄"]),
+        "배": ratio_of(doc, base["줄"], whole),
         "바탕판": fingerprint(base["줄"]),
     }
 
@@ -336,7 +373,34 @@ def unit(doc: dict, whole: Any, expand: Any, trail: tuple) -> dict[str, Any]:
 
 
 def head_of(doc: dict) -> str:
-    return f"1 {doc.get('단위')} 당"
+    """머리 띠 — 「1 본 당」 · 앞 수 있는 단위 = 「100본 당」."""
+    unit = str(doc.get("단위") or "")
+    return f"{unit} 당" if unit[:1].isdigit() else f"1 {unit} 당"
+
+
+def per_unit(got: dict, doc: dict) -> dict:
+    """화면 셈 답 줄 · 계 = SK 1 단위 몫(728-2) — 수량 · 금액 · 비목 ÷배(율 · 단가 그대로) ·
+    「식」 · 빈 단위(일위대가 줄 모드) = 옛 바탕 몫 그대로."""
+    times = got.get("배") or Decimal(1)
+    if times == 1 or str(doc.get("단위") or "").strip() in ("", "식"):
+        return got
+
+    def cut(v: Any) -> Any:
+        return None if v is None else Decimal(str(v)) / times
+
+    def one(x: dict) -> dict:
+        out = {**x, "금액": cut(x.get("금액"))}
+        if "율" not in x:
+            out["수량"] = cut(x.get("수량"))
+        if x.get("비목"):
+            out["비목"] = {k: cut(v) for k, v in x["비목"].items()}
+        if x.get("펼침"):
+            out["펼침"] = [one(y) for y in x["펼침"]]
+        return out
+
+    lines = [one(x) for x in got.get("줄") or []]
+    goods = [one(x) for x in got.get("재료") or []]
+    return {**got, "줄": lines, "재료": goods, "기준": got.get("1단위"), "화면배": times}
 
 
 # ── 저장 ──────────────────────────────────────────────────────────────
@@ -374,6 +438,7 @@ def clean_doc(doc: Any, here_: refs.Here) -> dict[str, Any]:
                 if cid in was:
                     one["원값"] = _was(was[cid])
         out["바탕판"] = fingerprint(base["줄"])
+        ratio_of(out, base["줄"], whole)  # 단위 못 바꿈(계수 없음) = 저장 막음(728-2)
         _stamp_adds(out, base, whole)
     except sd.DocError as e:
         raise _fail(e) from e
@@ -413,7 +478,7 @@ def calc_doc(doc: Any, given: dict | None = None) -> dict[str, Any]:
         got = run(clean, whole, given, trail=(me,), detail=True)
     except sd.DocError as e:
         raise _fail(e) from e
-    return labor._json({**got, "머리": head_of(clean)})
+    return labor._json({**per_unit(got, clean), "머리": head_of(clean)})
 
 
 def from_line(line: Any, name: str, unit: str) -> dict[str, Any]:
diff --git a/M02_MasterTemplete/M02_Sangeun_Doc.py b/M02_MasterTemplete/M02_Sangeun_Doc.py
index d8e47fb4e..477d07e35 100644
--- a/M02_MasterTemplete/M02_Sangeun_Doc.py
+++ b/M02_MasterTemplete/M02_Sangeun_Doc.py
@@ -10,7 +10,9 @@
              별도계상?(재료 · 없음 = 계 안)}
             | {종류: 로직, 로직, 입력값, 수량, 덮개?, 뺀줄?, 바탕판?}
             | {참조 | 고정, 이름?, 단위?, 수량}],
-     뺀줄 [cid], 바탕판}
+     뺀줄 [cid], 바탕판, 환산?}
+SK 단위 환산(728-2) = `환산` {계수: 양수}(성격 다름 · 바탕 앞 수 뗀 1 단위 = SK 몇 단위) |
+{단위중량: {종별, 형상}}(부피 ↔ 무게 · 표 CC000337) — 셈 = `M02_Sangeun_Calc.ratio_of`.
 둘째 기초(727-2) = 더한줄 로직 — 수량 = 그 기초 기준단위 몇 개 · `덮개` {세부 cid: 덮개} ·
 `뺀줄` [세부 cid](세부 cid = 그 기초 줄 `kind:키#n` · 화면 열쇠 `add:#k/세부 cid`) ·
 `바탕판` = 저장 때 서버가 그 기초 지문.
@@ -282,6 +284,8 @@ def clean(doc: Any, base_row: dict | None = None, whole: Any = None) -> dict[str
     out["입력값"], out["열린입력"] = given, opened
     if doc.get("켜쌓기율") is not None:
         out["켜쌓기율"] = plain(_num(doc["켜쌓기율"], "켜쌓기율"))
+    if doc.get("환산"):
+        out["환산"] = _swap_how(doc["환산"])
     picks = {}
     for cid, mt in (doc.get("고름") or {}).items():
         mt = str(mt or "")
@@ -304,6 +308,22 @@ def clean(doc: Any, base_row: dict | None = None, whole: Any = None) -> dict[str
     return out
 
 
+def _swap_how(raw: Any) -> dict[str, Any]:
+    """단위 환산 칸(728-2) — 계수(양수) · 단위중량 {종별, 형상} 중 있는 것만."""
+    if not isinstance(raw, dict):
+        raise DocError("환산이 묶음 아님")
+    out: dict[str, Any] = {}
+    if raw.get("계수") is not None:
+        coef = _num(raw["계수"], "환산 계수")
+        if coef <= 0:
+            raise DocError("환산 계수는 0 보다 커야 함")
+        out["계수"] = plain(coef)
+    pick = raw.get("단위중량")
+    if isinstance(pick, dict) and pick.get("종별") and pick.get("형상"):
+        out["단위중량"] = {k: str(pick[k]) for k in ("종별", "형상")}
+    return out
+
+
 def _marks(raw: Any) -> dict[str, dict[str, str]]:
     from M02_MasterTemplete import M02_Labor_Doc as labor
 
diff --git a/M02_MasterTemplete/logic/M02_Sangeun_Cover_Model.ts b/M02_MasterTemplete/logic/M02_Sangeun_Cover_Model.ts
index 0734af3ad..9a871b294 100644
--- a/M02_MasterTemplete/logic/M02_Sangeun_Cover_Model.ts
+++ b/M02_MasterTemplete/logic/M02_Sangeun_Cover_Model.ts
@@ -9,6 +9,7 @@
  *   일위대가 줄 → 이름 없는 SK 문서 = `lineDoc`(서버 `M02_Labor_Patch.as_doc` 꼴)
  *   둘째 기초(727-2) = 더한줄 로직 줄을 서버 `펼침`(세부 줄)으로 바꿔 놓음 · 열쇠 `add:#k/세부 cid` ·
  *   고침 = 그 더한줄의 `덮개` · `뺀줄`(품 = 화면 품 ÷ 수량 · 1 기준단위 몫) · 꼬리표 = 기초 둘 이상일 때만
+ *   SK 단위 환산(728-2) = 서버가 화면 줄을 SK 1 단위 몫으로(`화면배`) — 문서 품 = 화면 품 × 화면배(율 빼고)
  * 화면 · fetch · sessionStorage 없음(`CLAUDE.md` 4장).
  * ========================================================================== */
 
@@ -102,6 +103,9 @@ export interface SkAnswer {
   머리?: string;
   /** 바탕 원문번호(참조 바탕 = 그 키) */
   꼬리표?: string | null;
+  /** 바탕 기준단위 → SK 단위 배(728-2) · 화면 줄을 나눈 배(없으면 1 · 문서 품 = 화면 품 × 화면배) */
+  배?: number;
+  화면배?: number;
 }
 
 export interface CoverRow {
@@ -132,6 +136,8 @@ export interface CoverRow {
   apartPick: boolean;
   /** 둘째 기초 세부 줄 — 더한줄 차례 · 세부 cid · 수량(배) · 바탕 줄 · 그 밖 = null */
   sub: { k: number; cid: string; scale: number } | null;
+  /** 화면배(728-2) — 문서 품 = 화면 품 × t · `was` = 문서 몫 */
+  t: number;
 }
 
 /* ── 순수 셈 ── */
@@ -206,6 +212,7 @@ const near = (a: number | null | undefined, b: number | null | undefined): boole
 /** 셈 답 → 표 줄(엔진 줄 + 기준 밖 재료) */
 export function rowsOf(ans: SkAnswer, bare: SkAnswer | null, doc: SkDoc): CoverRow[] {
   const was = baseValues(bare);
+  const t = ans.화면배 ?? 1;
   const rows: CoverRow[] = [];
   const row = (
     cid: string,
@@ -227,7 +234,12 @@ export function rowsOf(ans: SkAnswer, bare: SkAnswer | null, doc: SkDoc): CoverR
     const cover = at ? owner?.덮개?.[at.cid] : added === null ? doc.덮개?.[cid] : undefined;
     const pct = (at?.cid ?? cid).startsWith("pct:");
     const keys = Object.keys(parts);
-    const base = at ? subWas(extra.바탕값) : added === null ? (was.get(cid) ?? null) : null;
+    const shown = added === null && !at ? (was.get(cid) ?? null) : null;
+    const base = at
+      ? subWas(extra.바탕값)
+      : shown && !pct && shown.qty != null
+        ? { ...shown, qty: shown.qty * t }
+        : shown;
     const old = cover?.원값;
     return {
       cid,
@@ -255,6 +267,7 @@ export function rowsOf(ans: SkAnswer, bare: SkAnswer | null, doc: SkDoc): CoverR
       priceEdit: !pct && (added === null || ["인력", "재료", "기계"].includes(String(one?.종류))),
       apartPick: one?.종류 === "재료",
       sub: at ? { ...at, scale: Number(owner?.수량 ?? 1) } : null,
+      t: pct ? 1 : t,
     };
   };
   for (const l of flatLines(ans)) rows.push(row(l.cid, l, partsOf(l), l));
@@ -301,14 +314,15 @@ export function setLineCover(doc: SkDoc, r: CoverRow, c: LineCover | null, opene
   if (r.added !== null) {
     const one = doc.더한줄?.[r.added];
     if (!one) return;
-    if (c?.qty != null) one.수량 = c.qty;
+    if (c?.qty != null) one.수량 = c.qty * r.t;
     if (price == null) delete one.단가;
     else one.단가 = price;
     return;
   }
   const cover: SkCover = {};
   // 세부 줄 품 = 화면 품 ÷ 더한줄 수량(1 기준단위 몫 · 수량 0 = 그대로)
-  const qty = r.sub && c?.qty != null && r.sub.scale ? c.qty / r.sub.scale : c?.qty;
+  const raw = c?.qty == null ? c?.qty : c.qty * r.t;
+  const qty = r.sub && raw != null && r.sub.scale ? raw / r.sub.scale : raw;
   const open = opened && !r.sub; // 열린입력 = 바탕 입력 — 세부 줄은 품 그대로
   // ponytail: 열린입력 배율 = 고친 품 ÷ 바탕 품(바탕 품 0 · 없음 = 품 고침 못 함)
   if (qty != null && open && r.was?.qty) cover.배율 = qty / r.was.qty;
@@ -445,6 +459,7 @@ export function hoView(
     });
   const lineBy = new Map(flatLines(ans).map((l) => [l.cid, l]));
   const tags = tagsOf(ans, doc);
+  const t = ans.화면배 ?? 1;
   const single = (l?: SkLine): string | undefined => {
     const parts = Object.entries(l?.비목 ?? {}).filter(([, v]) => v);
     return parts.length === 1 ? parts[0][0] : undefined;
@@ -479,7 +494,7 @@ export function hoView(
       요소: typeof a?.요소 === "string" ? a.요소 : "",
       이름: name,
       단위: l?.단위 ?? String(a?.단위 ?? ""),
-      수량: String(a?.수량 ?? l?.율 ?? l?.수량 ?? ""),
+      수량: String(a ? a.수량 / t : (l?.율 ?? l?.수량 ?? "")),
       비목: typeof a?.비목 === "string" ? a.비목 : single(l),
     };
     ho.push([cid, { ...(a ? made : ((known.get(cid) as HoItem) ?? made)), ...tag }]);
@@ -490,14 +505,15 @@ export function hoView(
     const hit = ADD_RE.exec(cid);
     const a = hit ? doc.더한줄?.[Number(hit[1])] : undefined;
     const part = PART_OF[String(a?.비목 ?? "")];
-    if (a) covers[i] = { qty: a.수량, ...(a.단가 != null && part ? { [part]: a.단가 } : {}) };
+    if (a) covers[i] = { qty: a.수량 / t, ...(a.단가 != null && part ? { [part]: a.단가 } : {}) };
     const at = subOf(cid);
     const owner = at ? doc.더한줄?.[at.k] : undefined;
     const c = hit ? undefined : at ? owner?.덮개?.[at.cid] : doc.덮개?.[cid];
     if (!c) return;
     const l = lineBy.get(cid);
     const out: LineCover = {};
-    if (c.qty != null) out.qty = at ? c.qty * Number(owner?.수량 ?? 1) : c.qty;
+    const per = (at?.cid ?? cid).startsWith("pct:") ? 1 : t; // 율 = 그대로
+    if (c.qty != null) out.qty = (at ? c.qty * Number(owner?.수량 ?? 1) : c.qty) / per;
     else if (c.배율 != null && l) out.qty = l.율 ?? l.수량 ?? undefined;
     for (const k of PARTS) if (c[k] != null) out[k] = c[k];
     covers[i] = out;
diff --git a/resources/tester/helper_728_2_cover_unit.cjs b/resources/tester/helper_728_2_cover_unit.cjs
new file mode 100644
index 000000000..934bede74
--- /dev/null
+++ b/resources/tester/helper_728_2_cover_unit.cjs
@@ -0,0 +1,44 @@
+/* PLAN 728-2 헬퍼 — SK 고침 꼴(`logic/M02_Sangeun_Cover_Model.ts`)이 화면배(SK 1 단위 몫)를 문서 몫으로 되돌리는지.
+ * 짝 = `test_728_2_sk_unit.py`. 결과 = 표준출력 JSON.
+ */
+const path = require("path");
+const { makeLoader } = require("./helper_ts_stub_loader.cjs");
+
+const ROOT = path.join(__dirname, "..", "..");
+const { load } = makeLoader({ root: ROOT });
+const m = load("M02_MasterTemplete", "logic", "M02_Sangeun_Cover_Model.ts");
+
+// GF000287 단목베기 SK 단위 본 — 서버 화면 답 = 100본 몫 ÷100(화면배 100)
+const line = (cid, 이름, 수량, 금액) => ({
+  cid,
+  이름,
+  단위: "인",
+  수량,
+  단가: 금액 / 수량,
+  금액,
+  비목: { 노무비: 금액 },
+});
+const ans = {
+  기준: { 계: 1538.894 },
+  줄: [line("labor:LB000101#0", "벌목부", 0.002, 506.486), line("add:#0", "보통인부", 0.5, 86034)],
+  정체: ["labor:LB000101#0", "add:#0"],
+  짝잃음: [],
+  바탕판: "",
+  배: 100,
+  화면배: 100,
+};
+const bare = { ...ans, 줄: [ans.줄[0]], 정체: ["labor:LB000101#0"] };
+const doc = {
+  단위: "본",
+  바탕: { 로직: "GF000287" },
+  더한줄: [{ 종류: "인력", 요소: "LB000002", 수량: 50 }],
+};
+const rows = m.rowsOf(ans, bare, doc);
+const out = { was: rows[0].was, t: rows.map((r) => r.t) };
+m.setLineCover(doc, rows[0], { qty: 0.003 }, false); // 화면 0.003 = 문서 0.3(100본 몫)
+m.setLineCover(doc, rows[1], { qty: 0.6 }, false); // 더한 인력 화면 0.6 = 문서 60
+out.cover = doc.덮개;
+out.added = doc.더한줄[0].수량;
+const view = m.hoView(ans, bare, null, doc);
+out.shown = view.covers;
+process.stdout.write(JSON.stringify(out));
diff --git a/resources/tester/test_715_sangeun_engine.py b/resources/tester/test_715_sangeun_engine.py
index 4961a6020..f7b17cdd9 100644
--- a/resources/tester/test_715_sangeun_engine.py
+++ b/resources/tester/test_715_sangeun_engine.py
@@ -46,7 +46,7 @@ def test_price_cover_is_hand_price_and_pct_follows():
 def test_bundle_cover_on_logic_line_partial():
     bare = labor.run_line(_whole(), SUB, {})
     sub = bare["줄"][2]
-    got = _run(바탕={"로직": SUB}, 덮개={"logic:GC000275#0": {"expense": 1000}})
+    got = _run(바탕={"로직": SUB}, 단위="주", 덮개={"logic:GC000275#0": {"expense": 1000}})
     line = got["줄"][2]
     qty = Decimal(str(sub["수량"]))
     assert line["비목"]["경비"] == pytest.approx(float(qty * 1000))
@@ -57,7 +57,7 @@ def test_bundle_cover_on_logic_line_partial():
 
 def test_untouched_lines_same_as_engine():
     bare = labor.run_line(_whole(), SUB, {})
-    got = _run(바탕={"로직": SUB})
+    got = _run(바탕={"로직": SUB}, 단위="주")  # 바탕 단위(728-2 — 성격 다르면 계수 칸)
     assert got["기준"]["계"] == pytest.approx(float(bare["기준"]["계"]))
 
 
diff --git a/resources/tester/test_727_sk_base_add.py b/resources/tester/test_727_sk_base_add.py
index 5bc9d0f35..8b4fda491 100644
--- a/resources/tester/test_727_sk_base_add.py
+++ b/resources/tester/test_727_sk_base_add.py
@@ -189,7 +189,13 @@ def test_727_3_옵션_저장_일위대가_그_옵션(world):  # noqa: F811
     assert float(up["기준"]["계"]) == pytest.approx(_m01(GF, rock), rel=1e-9)
     assert _m01(GF, rock) > _m01(GF, {"지역": "전국평균", "보정작업": "해당 없음"})
     # 둘째 기초 입력(바탕에 없는 이름)도 SK 입력값에 남고 그 옵션으로 셈
-    two = _sk(world["personal"], 바탕={"로직": PCT}, 더한줄=[{**SECOND, "로직": GF}], 입력값=rock)
+    two = _sk(  # 단위 = 바탕 단위(728-2 — 성격 다르면 계수 칸)
+        world["personal"],
+        바탕={"로직": PCT},
+        단위="㎡",
+        더한줄=[{**SECOND, "로직": GF}],
+        입력값=rock,
+    )
     assert two["입력값"] == rock
     got = _run(world["personal"], two)
     assert _line(got, "add:#0")["금액"] == pytest.approx(_m01(GF, rock), rel=1e-9)
diff --git a/resources/tester/test_728_2_sk_unit.py b/resources/tester/test_728_2_sk_unit.py
new file mode 100644
index 000000000..545e47808
--- /dev/null
+++ b/resources/tester/test_728_2_sk_unit.py
@@ -0,0 +1,124 @@
+"""728-2 지킴 — SK 단위 환산: 바탕 기준단위 → SK 단위 배 · 화면 줄 · 계 = SK 1 단위 몫 ·
+계수 없으면 셈 막음 · 「식」 = 옛 셈 · 둘째 기초 수량 처음값 · 돈 아닌 기초 고르기 창에서 뺌 ·
+고침 꼴 화면배 되돌림."""
+
+from __future__ import annotations
+
+import json
+import subprocess
+import sys
+from decimal import Decimal
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+HERE = Path(__file__).resolve().parent
+sys.path.insert(0, str(ROOT))
+sys.path.insert(0, str(ROOT / "resources/master_data/scripts"))
+
+import master_unit as mu  # noqa: E402
+
+from M01_MasterData import M01_MasterData_Store as m01  # noqa: E402
+from M02_MasterTemplete import M02_Sangeun_Calc as sc  # noqa: E402
+from M02_MasterTemplete import M02_Sangeun_Doc as sd  # noqa: E402
+
+
+@pytest.fixture(scope="module")
+def whole():
+    return m01.loaded()[1]
+
+
+def _doc(base, unit, **more):
+    return {"키": "SK-999999", "이름": "sub3임시", "단위": unit, "바탕": {"로직": base}, **more}
+
+
+def _shown(whole, doc):
+    clean = sd.clean(doc, None, whole)
+    return sc.per_unit(sc.run(clean, whole), clean)
+
+
+def test_단목베기_100본_제안_본으로_바꾸면_1본_계(whole):
+    full = _shown(whole, _doc("GF000287", "100본"))
+    assert full["배"] == 1 and round(full["기준"]["계"], 2) == Decimal("153889.40")
+    assert sc.head_of({"단위": "100본"}) == "100본 당"
+    one = _shown(whole, _doc("GF000287", "본"))
+    assert one["배"] == 100 and round(one["기준"]["계"], 2) == Decimal("1538.89")
+    assert sc.head_of({"단위": "본"}) == "1 본 당"
+    pairs = [(x["수량"], y["수량"]) for x, y in zip(full["줄"], one["줄"], strict=True)]
+    assert all(b == a / 100 for a, b in pairs) and one["화면배"] == 100  # 세부 품 ÷100
+
+
+def test_사석_수상고르기_10제곱미터_에서_1제곱미터(whole):
+    one = _shown(whole, _doc("GC000421", "㎡"))
+    assert round(one["기준"]["계"], 2) == Decimal("44791.32")
+
+
+def test_성격_다르면_계수_칸_없으면_셈_막음(whole):
+    with pytest.raises(sd.DocError, match="환산 계수"):
+        _shown(whole, _doc("GF000099", "m"))
+    base = _shown(whole, _doc("GF000099", "㎥"))["기준"]["계"]
+    two = _shown(whole, _doc("GF000099", "m", 환산={"계수": 2}))
+    assert two["배"] == 2 and two["기준"]["계"] == base / 2
+    with pytest.raises(sd.DocError, match="단위중량"):
+        _shown(whole, _doc("GF000099", "톤"))
+    rock = _shown(
+        whole, _doc("GF000099", "톤", 환산={"단위중량": {"종별": "암석", "형상": "화강암"}})
+    )
+    assert rock["배"] == Decimal("2.7")  # 1 ㎥ = 2.7 톤(2,700 ㎏/㎥)
+    with pytest.raises(sd.DocError, match="0 보다"):
+        sd.clean(_doc("GF000099", "m", 환산={"계수": 0}), None, whole)
+
+
+def test_식_빈_단위는_옛_셈(whole):
+    old = _shown(whole, _doc("GF000287", "식"))
+    assert old["배"] == 100 and round(old["1단위"]["계"], 2) == Decimal("1538.89")
+    assert "화면배" not in old and old["기준"]["계"] == Decimal("153889.4")  # 화면 = 바탕 몫 그대로
+
+
+def test_둘째_기초_수량_처음값_배(whole):
+    """바탕 10㎡(GC000421) + 둘째 기초 100㎡(GF000041) — 처음값 0.1 = 바탕 기준단위 몫."""
+    qty = mu.swap("10㎡", "100㎡")["배"]
+    assert qty == Decimal("0.1")
+    alone = sc.run(sd.clean(_doc("GF000041", "100㎡"), None, whole), whole)["1단위"]["계"]
+    one = {"종류": "로직", "로직": "GF000041", "입력값": {}, "수량": float(qty)}
+    got = sc.run(sd.clean(_doc("GC000421", "㎡", 더한줄=[one]), None, whole), whole)
+    bare = sc.run(sd.clean(_doc("GC000421", "㎡"), None, whole), whole)
+    added = got["1단위"]["계"] - bare["1단위"]["계"]
+    assert abs(added - alone * qty / 10) < Decimal("0.01")  # ㎡ 몫 = 100㎡ 값 ÷100
+    src = (ROOT / "M02_MasterTemplete/M02_MasterTemplete_Sangeun_Detail.ts").read_text(
+        encoding="utf-8"
+    )
+    assert "swapUnit(" in src and "addBase(" in src and "baseUnitOf(" in src
+
+
+def test_돈_아닌_기초_고르기_창에서_뺌(whole):
+    money = [
+        r
+        for tid, d in whole.index.items()
+        if tid in ("GC", "GF", "QC", "QF")
+        for r in d.values()
+        if isinstance(r, dict)
+        and "결과단위" in r
+        and not str(r["결과단위"]).strip().startswith("원")
+    ]
+    assert len(money) == 21
+    src = (ROOT / "M02_MasterTemplete/M02_MasterTemplete_Find_Pick.ts").read_text(encoding="utf-8")
+    assert '!logic.결과단위.trim().startsWith("원")' in src
+
+
+def test_고침_꼴_화면배_되돌림():
+    proc = subprocess.run(  # noqa: S603 — 고정 실행 파일
+        ["node", str(HERE / "helper_728_2_cover_unit.cjs")],
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        timeout=60,
+    )
+    assert proc.returncode == 0, proc.stderr
+    out = json.loads(proc.stdout)
+    assert out["was"]["qty"] == pytest.approx(0.2)  # 바탕 값 = 문서 몫(100본)
+    assert out["cover"]["labor:LB000101#0"]["qty"] == pytest.approx(0.3)
+    assert out["added"] == pytest.approx(60)
+    assert out["shown"]["0"]["qty"] == pytest.approx(0.003)  # 다시 그리면 화면 몫
+    assert out["shown"]["1"]["qty"] == pytest.approx(0.6)
diff --git a/ui_template/ui_template_locale_m2.ts b/ui_template/ui_template_locale_m2.ts
index a25a1bf7a..b8fb14c9c 100644
--- a/ui_template/ui_template_locale_m2.ts
+++ b/ui_template/ui_template_locale_m2.ts
@@ -203,6 +203,9 @@ export const ui_locales_m2 = {
   M02_SangeunRemoved: ["뺀 줄", "Removed rows"],
   M02_SangeunUnit: ["단위(1 단위 값)", "Unit (value per 1)"],
   M02_SangeunNeed: ["비우면 저장 안 됨", "Required"],
+  M02_SangeunSwapCoef: ["환산 계수", "Conversion factor"],
+  M02_SangeunSwapWeight: ["단위중량", "Unit weight"],
+  M02_SangeunSwapPick: ["고르세요", "Choose"],
   M02_SangeunAddLine: ["항목 추가", "Add item"],
   M02_SangeunDrop: ["빼기", "Remove"],
   M02_SangeunDropBase: ["기초 빼기", "Remove base"],