diff --git a/internal/processor/purchase_order_processor.go b/internal/processor/purchase_order_processor.go
index 7d87e90..169ffe9 100644
--- a/internal/processor/purchase_order_processor.go
+++ b/internal/processor/purchase_order_processor.go
@@ -107,7 +107,7 @@ func (p *PurchaseOrderProcessorImpl) CreatePurchaseOrder(ctx context.Context, or
 	// Calculate total amount
 	totalAmount := 0.0
 	for _, item := range req.Items {
-		totalAmount += item.Amount
+		totalAmount += calculatePurchaseOrderItemTotal(item.Quantity, item.Amount)
 	}
 
 	// Create purchase order entity
@@ -277,7 +277,7 @@ func (p *PurchaseOrderProcessorImpl) UpdatePurchaseOrder(ctx context.Context, id
 				UnitID:             unitID,
 				Amount:             amount,
 			}
-			totalAmount += amount
+			totalAmount += calculatePurchaseOrderItemTotal(quantity, amount)
 		}
 
 		// Delete and recreate only after all replacement items are valid.
@@ -447,7 +447,7 @@ func (p *PurchaseOrderProcessorImpl) UpdatePurchaseOrderStatus(ctx context.Conte
 			// Calculate unit cost in ingredient's base unit
 			unitCost := 0.0
 			if quantityToAdd > 0 {
-				unitCost = item.Amount / quantityToAdd
+				unitCost = calculatePurchaseOrderItemTotal(item.Quantity, item.Amount) / quantityToAdd
 			}
 
 			// Create inventory movement for ingredient purchase
@@ -506,3 +506,11 @@ func (p *PurchaseOrderProcessorImpl) validatePurchaseCategory(ctx context.Contex
 
 	return category, nil
 }
+
+func calculatePurchaseOrderItemTotal(quantity *float64, amount float64) float64 {
+	if quantity == nil {
+		return amount
+	}
+
+	return *quantity * amount
+}