diff --git a/app/modules/cupang/router.py b/app/modules/cupang/router.py
index aeb5a04..832a8d4 100644
--- a/app/modules/cupang/router.py
+++ b/app/modules/cupang/router.py
@@ -568,6 +568,102 @@ async def box_rule_delete(
     return RedirectResponse(url="/cupang/box-rules", status_code=303)
 
 
+# ════════════════════════════════════════════════════════════
+# 박스 계산기 — 제품명 + 수량 → 박스 수 / 남은 낱개
+#   저장하지 않는 계산 전용 화면. 규칙은 cupang_box_rules 를 그대로 사용한다.
+# ════════════════════════════════════════════════════════════
+@router.get("/box-calc", response_class=HTMLResponse)
+async def box_calc_page(request: Request) -> HTMLResponse:
+    from app.main import build_erp_nav, render_template  # noqa: WPS433
+    from app.store import is_admin  # noqa: WPS433
+
+    guard = _guard(request)
+    if not isinstance(guard, tuple):
+        return guard
+    store, user = guard
+    return render_template(
+        request,
+        "cupang/box_calc.html",
+        {
+            "user": user,
+            "is_admin": is_admin(user),
+            "nav_items": build_erp_nav(user, active="cupang"),
+            "page_title": "쿠팡 밀크런 — 박스 계산",
+            "page_subtitle": "제품명과 수량을 넣으면 박스 수와 남은 낱개를 계산합니다.",
+            "box_rules": store.list_box_rules(),
+        },
+    )
+
+
+@router.post("/api/box-calc")
+async def box_calc_api(
+    request: Request,
+    payload: dict[str, Any] = Body(...),
+    user: dict[str, Any] = Depends(_require_user),
+) -> JSONResponse:
+    """[{product_code, quantity}] → 제품별 박스 계산 + 박스명별 합계.
+
+    클라이언트 계산을 신뢰하지 않고 store.compute_boxes 로 서버에서 계산한다.
+    """
+    from .store import compute_boxes  # noqa: WPS433
+
+    store = _store(request)
+    if store is None:
+        raise HTTPException(status_code=503, detail="cupang_db 미설정")
+
+    raw_items = payload.get("items")
+    if not isinstance(raw_items, list):
+        raise HTTPException(status_code=400, detail="items 는 배열이어야 합니다.")
+
+    rules = {r["product_code"]: r for r in store.list_box_rules()}
+
+    results: list[dict[str, Any]] = []
+    totals: dict[str, dict[str, Any]] = {}
+    for raw in raw_items:
+        if not isinstance(raw, dict):
+            continue
+        code = str(raw.get("product_code") or "").strip()
+        if not code:
+            continue
+        try:
+            qty = int(raw.get("quantity") or 0)
+        except (TypeError, ValueError):
+            qty = 0
+        qty = max(qty, 0)
+
+        rule = rules.get(code)
+        upb = rule["units_per_box"] if rule else None
+        calc = compute_boxes(qty, upb)
+        box_name = (rule or {}).get("box_name") or ""
+        results.append(
+            {
+                "product_code": code,
+                "product_name": (rule or {}).get("product_name_snapshot") or code,
+                "box_name": box_name,
+                "units_per_box": calc["units_per_box"],
+                "quantity": qty,
+                "configured": calc["configured"],
+                "full_boxes": calc["full_boxes"],
+                "remainder_units": calc["remainder_units"],
+                "required_boxes": calc["required_boxes"],
+            }
+        )
+        if calc["configured"]:
+            agg = totals.setdefault(
+                box_name, {"box_name": box_name, "full_boxes": 0, "required_boxes": 0, "remainder_units": 0}
+            )
+            agg["full_boxes"] += calc["full_boxes"]
+            agg["required_boxes"] += calc["required_boxes"]
+            agg["remainder_units"] += calc["remainder_units"]
+
+    return JSONResponse(
+        {
+            "results": results,
+            "totals": sorted(totals.values(), key=lambda t: t["box_name"]),
+        }
+    )
+
+
 # ════════════════════════════════════════════════════════════
 # 설정 — 제품명 카탈로그 관리 (itemcode_db 에서 등록)
 # ════════════════════════════════════════════════════════════
diff --git a/app/modules/cupang/templates/cupang/box_calc.html b/app/modules/cupang/templates/cupang/box_calc.html
new file mode 100644
index 0000000..bcde74e
--- /dev/null
+++ b/app/modules/cupang/templates/cupang/box_calc.html
@@ -0,0 +1,225 @@
+{% extends "erp_base.html" %}
+
+{% block head_extra %}<link rel="stylesheet" href="/static/cupang.css?v=20260828s" />{% endblock %}
+
+{% block content %}
+<section class="cpg">
+
+  <div class="erp-page-actions">
+    <a class="erp-btn erp-btn-primary" href="/cupang/">◀◀ 달력</a>
+    <a class="erp-btn erp-btn-outline" href="/cupang/box-rules">박스 입수량 설정</a>
+  </div>
+
+  {% if not box_rules %}
+  <div class="erp-card cpg-form-card">
+    <p class="erp-muted">
+      등록된 박스 입수량 규칙이 없습니다.
+      <a href="/cupang/box-rules">박스 입수량 설정</a>에서 먼저 제품별 입수량을 등록하세요.
+    </p>
+  </div>
+  {% else %}
+
+  <div class="erp-card cpg-form-card cpg-calc-card">
+    <div class="cpg-card-head">
+      <h2>박스 계산</h2>
+      <span class="erp-muted">수량을 고치고 다시 계산하면 결과가 갱신됩니다.</span>
+    </div>
+
+    <div class="erp-table-wrap">
+      <table class="erp-table cpg-calc-table">
+        <thead>
+          <tr>
+            <th>제품명</th>
+            <th class="cpg-calc-num">수량</th>
+            <th>박스명</th>
+            <th class="cpg-calc-num">입수량</th>
+            <th class="cpg-calc-num">박스 수</th>
+            <th class="cpg-calc-num">남은 낱개</th>
+            <th class="cpg-calc-num">총 필요 박스</th>
+            <th>동작</th>
+          </tr>
+        </thead>
+        <tbody id="cpg-calc-rows"></tbody>
+      </table>
+    </div>
+
+    <div class="erp-page-actions cpg-calc-actions">
+      <button type="button" class="erp-btn erp-btn-primary" id="cpg-calc-run">계산 / 재계산</button>
+      <button type="button" class="erp-btn erp-btn-outline" id="cpg-calc-add">+ 제품 추가</button>
+      <button type="button" class="erp-btn erp-btn-outline" id="cpg-calc-reset">초기화</button>
+      <span class="erp-muted" id="cpg-calc-msg"></span>
+    </div>
+  </div>
+
+  <div class="erp-card cpg-form-card cpg-calc-sum" id="cpg-calc-sum-card" hidden>
+    <div class="cpg-card-head">
+      <h2>박스명별 합계</h2>
+      <span class="erp-muted">가득 채운 박스 / 낱개 포함 총 필요 박스</span>
+    </div>
+    <div class="erp-table-wrap">
+      <table class="erp-table">
+        <thead>
+          <tr>
+            <th>박스명</th>
+            <th class="cpg-calc-num">박스 수</th>
+            <th class="cpg-calc-num">남은 낱개 합</th>
+            <th class="cpg-calc-num">총 필요 박스</th>
+          </tr>
+        </thead>
+        <tbody id="cpg-calc-sum-rows"></tbody>
+      </table>
+    </div>
+  </div>
+
+  <script type="application/json" id="cpg-calc-rules">{{ box_rules | tojson }}</script>
+  <script>
+  // 박스 계산기 — 행 추가/삭제, 수량 수정 후 재계산.
+  // 계산 자체는 서버(POST /cupang/api/box-calc, store.compute_boxes)에서 수행한다.
+  (function () {
+    var tbody = document.getElementById("cpg-calc-rows");
+    if (!tbody) return;
+    var runBtn = document.getElementById("cpg-calc-run");
+    var addBtn = document.getElementById("cpg-calc-add");
+    var resetBtn = document.getElementById("cpg-calc-reset");
+    var msg = document.getElementById("cpg-calc-msg");
+    var sumCard = document.getElementById("cpg-calc-sum-card");
+    var sumRows = document.getElementById("cpg-calc-sum-rows");
+
+    var rules = [];
+    try { rules = JSON.parse(document.getElementById("cpg-calc-rules").textContent || "[]"); } catch (e) {}
+
+    var optionsHtml = '<option value="">— 제품명 선택 —</option>';
+    rules.forEach(function (r) {
+      var label = (r.product_name_snapshot || r.product_code) +
+                  " (" + (r.box_name || "-") + " / " + r.units_per_box + "개)";
+      optionsHtml += '<option value="' + esc(r.product_code) + '">' + esc(label) + "</option>";
+    });
+
+    function esc(s) { var d = document.createElement("div"); d.textContent = s == null ? "" : s; return d.innerHTML; }
+
+    function addRow(code, qty) {
+      var tr = document.createElement("tr");
+      tr.className = "cpg-calc-row";
+      tr.innerHTML =
+        '<td><select class="erp-select cpg-calc-name">' + optionsHtml + "</select></td>" +
+        '<td class="cpg-calc-num"><input class="erp-input cpg-calc-qty" type="number" min="0" step="1" value="' + (qty || 0) + '" /></td>' +
+        '<td class="cpg-calc-box">—</td>' +
+        '<td class="cpg-calc-num cpg-calc-upb">—</td>' +
+        '<td class="cpg-calc-num cpg-calc-boxes">—</td>' +
+        '<td class="cpg-calc-num cpg-calc-rem">—</td>' +
+        '<td class="cpg-calc-num cpg-calc-req">—</td>' +
+        '<td><button type="button" class="erp-btn erp-btn-danger cpg-calc-del">삭제</button></td>';
+      tbody.appendChild(tr);
+      if (code) tr.querySelector(".cpg-calc-name").value = code;
+      return tr;
+    }
+
+    function clearResults() {
+      Array.prototype.forEach.call(tbody.querySelectorAll(".cpg-calc-row"), function (tr) {
+        tr.querySelector(".cpg-calc-box").textContent = "—";
+        tr.querySelector(".cpg-calc-upb").textContent = "—";
+        tr.querySelector(".cpg-calc-boxes").textContent = "—";
+        tr.querySelector(".cpg-calc-rem").textContent = "—";
+        tr.querySelector(".cpg-calc-req").textContent = "—";
+        tr.classList.remove("cpg-calc-warn");
+      });
+      sumCard.hidden = true;
+      sumRows.innerHTML = "";
+    }
+
+    function collect() {
+      var items = [];
+      Array.prototype.forEach.call(tbody.querySelectorAll(".cpg-calc-row"), function (tr) {
+        var code = tr.querySelector(".cpg-calc-name").value;
+        if (!code) return;
+        items.push({ product_code: code, quantity: parseInt(tr.querySelector(".cpg-calc-qty").value, 10) || 0, _tr: tr });
+      });
+      return items;
+    }
+
+    function run() {
+      var items = collect();
+      if (!items.length) { clearResults(); msg.textContent = "제품명을 하나 이상 선택하세요."; return; }
+      msg.textContent = "계산 중…";
+      runBtn.disabled = true;
+      fetch("/cupang/api/box-calc", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ items: items.map(function (it) { return { product_code: it.product_code, quantity: it.quantity }; }) })
+      })
+        .then(function (r) { if (!r.ok) throw new Error("http " + r.status); return r.json(); })
+        .then(function (data) {
+          var results = (data && data.results) || [];
+          results.forEach(function (res, i) {
+            var tr = items[i] && items[i]._tr;
+            if (!tr) return;
+            tr.querySelector(".cpg-calc-box").textContent = res.box_name || "—";
+            tr.querySelector(".cpg-calc-upb").textContent = res.units_per_box ? res.units_per_box + "개" : "미설정";
+            if (res.configured) {
+              tr.querySelector(".cpg-calc-boxes").textContent = res.full_boxes + "박스";
+              tr.querySelector(".cpg-calc-rem").textContent = res.remainder_units + "개";
+              tr.querySelector(".cpg-calc-req").textContent = res.required_boxes + "박스";
+              tr.classList.remove("cpg-calc-warn");
+            } else {
+              tr.querySelector(".cpg-calc-boxes").textContent = "—";
+              tr.querySelector(".cpg-calc-rem").textContent = "—";
+              tr.querySelector(".cpg-calc-req").textContent = "—";
+              tr.classList.add("cpg-calc-warn");
+            }
+          });
+          var totals = (data && data.totals) || [];
+          if (totals.length) {
+            var html = "";
+            totals.forEach(function (t) {
+              html += "<tr><td>" + esc(t.box_name || "—") + "</td>" +
+                      '<td class="cpg-calc-num">' + t.full_boxes + "박스</td>" +
+                      '<td class="cpg-calc-num">' + t.remainder_units + "개</td>" +
+                      '<td class="cpg-calc-num">' + t.required_boxes + "박스</td></tr>";
+            });
+            sumRows.innerHTML = html;
+            sumCard.hidden = false;
+          } else {
+            sumCard.hidden = true;
+          }
+          msg.textContent = "계산 완료 (" + results.length + "건)";
+        })
+        .catch(function () { msg.textContent = "계산 실패 — 새로고침 후 다시 시도하세요."; })
+        .then(function () { runBtn.disabled = false; });
+    }
+
+    tbody.addEventListener("click", function (e) {
+      var del = e.target.closest(".cpg-calc-del");
+      if (!del) return;
+      var rows = tbody.querySelectorAll(".cpg-calc-row");
+      if (rows.length <= 1) { addRow("", 0); }
+      del.closest("tr").remove();
+      msg.textContent = "";
+    });
+
+    // 수량/제품을 바꾸면 이전 결과는 지운다 — 낡은 숫자 오독 방지.
+    tbody.addEventListener("input", function (e) {
+      if (e.target.classList.contains("cpg-calc-qty")) { msg.textContent = "수량 변경됨 — 재계산하세요."; }
+    });
+    tbody.addEventListener("change", function (e) {
+      if (e.target.classList.contains("cpg-calc-name")) { msg.textContent = "제품 변경됨 — 재계산하세요."; }
+    });
+    tbody.addEventListener("keydown", function (e) {
+      if (e.key === "Enter" && e.target.classList.contains("cpg-calc-qty")) { e.preventDefault(); run(); }
+    });
+
+    runBtn.addEventListener("click", run);
+    addBtn.addEventListener("click", function () { addRow("", 0); });
+    resetBtn.addEventListener("click", function () {
+      tbody.innerHTML = "";
+      addRow("", 0);
+      clearResults();
+      msg.textContent = "";
+    });
+
+    addRow("", 0);
+  })();
+  </script>
+  {% endif %}
+
+</section>
+{% endblock %}
diff --git a/app/modules/cupang/templates/cupang/index.html b/app/modules/cupang/templates/cupang/index.html
index 1cc50dc..a835994 100644
--- a/app/modules/cupang/templates/cupang/index.html
+++ b/app/modules/cupang/templates/cupang/index.html
@@ -13,6 +13,7 @@
         <a class="erp-btn erp-btn-outline" href="/cupang/products">제품명 설정</a>
         <a class="erp-btn erp-btn-outline" href="/cupang/centers">입고센터 관리</a>
         <a class="erp-btn erp-btn-outline" href="/cupang/box-rules">박스 입수량 설정</a>
+        <a class="erp-btn erp-btn-outline" href="/cupang/box-calc">박스 계산</a>
       </span>
     </div>
     <div class="cpg-actions-spacer"></div>
diff --git a/app/static/cupang.css b/app/static/cupang.css
index 2131c52..c52413e 100644
--- a/app/static/cupang.css
+++ b/app/static/cupang.css
@@ -326,3 +326,12 @@
 }
 .cpg-sort.is-asc .cpg-sort-ind::after  { content: "▲"; opacity: 1; }
 .cpg-sort.is-desc .cpg-sort-ind::after { content: "▼"; opacity: 1; }
+
+/* 박스 계산기 */
+.cpg-calc-table .cpg-calc-num { text-align: right; white-space: nowrap; }
+.cpg-calc-table th.cpg-calc-num { text-align: right; }
+.cpg-calc-table .cpg-calc-name { min-width: 240px; }
+.cpg-calc-table .cpg-calc-qty { width: 96px; text-align: right; }
+.cpg-calc-row.cpg-calc-warn { background: color-mix(in srgb, var(--color-callout-red) 8%, transparent); }
+.cpg-calc-actions { margin-top: 12px; gap: 8px; align-items: center; }
+.cpg-calc-sum { margin-top: 16px; }