diff --git a/services/reportService.js b/services/reportService.js
new file mode 100644
index 0000000..88eb904
--- /dev/null
+++ b/services/reportService.js
@@ -0,0 +1,146 @@
+'use strict';
+
+/**
+ * reportService.js
+ * Rapor hesaplama motoru — kategori bazlı raporlar, stok değerleri ve hareket özetleri.
+ * Saf fonksiyonlar; test edilebilir, route'tan bağımsız.
+ */
+
+const productModel = require('../models/productModel');
+const stockModel = require('../models/stockModel');
+const categoryModel = require('../models/categoryModel');
+
+/** ISO tarihini Date nesnesine güvenle çevirir (geçersizse boş aralık dönmez). */
+function toDate(value) {
+  const d = value ? new Date(value) : null;
+  return d && !isNaN(d.getTime()) ? d : null;
+}
+
+/**
+ * Belirli bir kategoriye ait ürünlerin toplam stok değerini hesaplar.
+ * @param {number} categoryId kategori ID
+ * @returns {number} toplam değer (stock * unitPrice)
+ */
+function valueByCategory(categoryId) {
+  const categories = categoryModel.readAll();
+  const catId = Number(categoryId);
+
+  // id:0 / 'all' => tüm kategoriler
+  if (catId === 0 || String(categoryId).toLowerCase() === 'all') {
+    const products = productModel.readAll();
+    return products.reduce((sum, p) => sum + Number(p.stock) * Number(p.unitPrice), 0);
+  }
+
+  const cat = categories.find((c) => c.id === catId);
+  if (!cat) return 0;
+
+  const products = productModel.findByCategory(catId);
+  return products.reduce((sum, p) => sum + Number(p.stock) * Number(p.unitPrice), 0);
+}
+
+/**
+ * Tarih aralığında kategori ürünlerine ait giriş/çıkış özeti.
+ * @param {number|null} categoryId kategori ID (0/null = hepsi)
+ * @param {string} fromDate başlangıç tarihi (ISO)
+ * @param {string} toDate bitiş tarihi (ISO)
+ * @returns {Object} {in, out, net}
+ */
+function movementSummary(categoryId = null, fromDate = '', toDate = '') {
+  const from = toDate(fromDate);
+  const to = toDate(toDate);
+
+  // Kategoriye ait ürün ID'lerini bul
+  let productIds = new Set();
+  const catId = Number(categoryId);
+  if (catId && !isNaN(catId) && catId !== 0) {
+    productModel.findByCategory(catId).forEach((p) => productIds.add(Number(p.id)));
+  } else {
+    productModel.readAll().forEach((p) => productIds.add(Number(p.id)));
+  }
+
+  const movements = stockModel.readAll().filter((m) => {
+    if (!productIds.has(Number(m.productId))) return false;
+    const d = new Date(m.date);
+    if (from && d < from) return false;
+    if (to) {
+      // to bitiş gününü kapsar
+      const toEnd = new Date(to);
+      toEnd.setHours(23, 59, 59, 999);
+      if (d > toEnd) return false;
+    }
+    return true;
+  });
+
+  let inQty = 0;
+  let outQty = 0;
+  for (const m of movements) {
+    if (m.type === 'in') inQty += Number(m.quantity) || 0;
+    else if (m.type === 'out') outQty += Number(m.quantity) || 0;
+  }
+
+  return { in: inQty, out: outQty, net: inQty - outQty, movements };
+}
+
+/**
+ * Kategori bazlı tam rapor.
+ * @param {number|null} categoryId kategori ID
+ * @param {Object} opts {fromDate, toDate}
+ * @returns {Object} {category, totalProducts, totalStockValue, incomingQty, outgoingQty, movements, lowStockCount}
+ */
+function categoryReport(categoryId = null, opts = {}) {
+  const { fromDate = '', toDate = '' } = opts || {};
+  const catId = Number(categoryId);
+  const categories = categoryModel.readAll();
+  const category =
+    (catId && categories.find((c) => c.id === catId)) ||
+    (String(categoryId).toLowerCase() === 'all' ? { id: 0, name: 'Tümü' } : null);
+
+  const products = category && category.id !== 0
+    ? productModel.findByCategory(catId)
+    : productModel.readAll();
+
+  const totalStockValue = products.reduce((s, p) => s + Number(p.stock) * Number(p.unitPrice), 0);
+  const summary = movementSummary(catId || 0, fromDate, toDate);
+
+  return {
+    category,
+    totalProducts: products.length,
+    totalStockValue,
+    incomingQty: summary.in,
+    outgoingQty: summary.out,
+    netQty: summary.net,
+    movements: summary.movements,
+    lowStockCount: products.filter(
+      (p) => Number(p.stock) <= (Number(p.minimumStock) || 10)
+    ).length
+  };
+}
+
+/**
+ * Tüm kategorilerin özet raporları (dashboard / rapor sayfası tablosu).
+ * @returns {Array} [{id, name, totalProducts, totalStockValue, lowStockCount}]
+ */
+function allCategorySummary() {
+  const categories = categoryModel.readAll();
+  return categories.map((cat) => {
+    const products = productModel.findByCategory(cat.id);
+    const totalStockValue = products.reduce((s, p) => s + Number(p.stock) * Number(p.unitPrice), 0);
+    return {
+      id: cat.id,
+      name: cat.name,
+      slug: cat.slug,
+      totalProducts: products.length,
+      totalStockValue,
+      lowStockCount: products.filter(
+        (p) => Number(p.stock) <= (Number(p.minimumStock) || 10)
+      ).length
+    };
+  });
+}
+
+module.exports = {
+  categoryReport,
+  valueByCategory,
+  movementSummary,
+  allCategorySummary
+};