diff --git a/service/models/shop_cart.py b/service/models/shop_cart.py
index 5dc7eda..c75c05d 100644
--- a/service/models/shop_cart.py
+++ b/service/models/shop_cart.py
@@ -88,6 +88,18 @@ def deserialize(self, data):
             ) from error
         return self
 
+    def update_total_price(self):
+        """
+        update the total price of a ShopCart
+        """
+        price = 0
+        for item in self.items:
+            if item.price is not None and item.quantity is not None:
+                price += item.price * item.quantity
+
+        self.total_price = price
+        self.update()
+
     ##################################################
     # CLASS METHODS
     ##################################################
diff --git a/service/routes.py b/service/routes.py
index 73c6139..bf8b575 100644
--- a/service/routes.py
+++ b/service/routes.py
@@ -190,6 +190,8 @@ def create_shopcart_item(shopcart_id):
     # Append item to the shopcart
     shopcart.items.append(item)
     shopcart.update()
+    # update the total price
+    shopcart.update_total_price()
 
     # Create a message to return
     message = item.serialize()
@@ -243,6 +245,15 @@ def delete_shopcart_items(shopcart_id, item_id):
     if item:
         item.delete()
 
+        # update the total price
+        shopcart = ShopCart.find(shopcart_id)
+        if not shopcart:
+            abort(
+                status.HTTP_404_NOT_FOUND,
+                f"ShopCart with ID '{shopcart_id}' could not be found",
+            )
+        shopcart.update_total_price()
+
     return "", status.HTTP_204_NO_CONTENT
 
 
@@ -274,6 +285,14 @@ def update_shopcart_item(shopcart_id, item_id):
     item.id = item_id
     item.update()
 
+    shopcart = ShopCart.find(shopcart_id)
+    if not shopcart:
+        abort(
+            status.HTTP_404_NOT_FOUND,
+            f"ShopCart with ID '{shopcart_id}' could not be found",
+        )
+    shopcart.update_total_price()
+
     return jsonify(item.serialize()), status.HTTP_200_OK
 
 
diff --git a/tests/test_routes.py b/tests/test_routes.py
index ebac58c..00ee823 100644
--- a/tests/test_routes.py
+++ b/tests/test_routes.py
@@ -473,3 +473,118 @@ def test_bad_request(self):
         """It should not Create when sending the wrong data"""
         resp = self.client.post(BASE_URL, json={"name": "not enough data"})
         self.assertEqual(resp.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_shopcart_total_price_with_new_item(self):
+        """
+        It should update the shopcart total price
+        once a new item is added
+        """
+        shop_cart = self._create_shopcarts(1)[0]
+        item_1 = ShopCartItemFactory()
+        resp = self.client.post(
+            f"{BASE_URL}/{shop_cart.id}/items",
+            json=item_1.serialize(),
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+
+        item_2 = ShopCartItemFactory()
+        resp = self.client.post(
+            f"{BASE_URL}/{shop_cart.id}/items",
+            json=item_2.serialize(),
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+
+        resp = self.client.get(
+            f"{BASE_URL}/{shop_cart.id}", content_type="application/json"
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        data = resp.get_json()
+        self.assertEqual(
+            data["total_price"],
+            str(item_1.price * item_1.quantity + item_2.price * item_2.quantity),
+        )
+
+    def test_shopcart_total_price_with_delete_item(self):
+        """
+        It should update the shopcart total price
+        once an item is deleted
+        """
+        shopcart = self._create_shopcarts(1)[0]
+        # add the first item
+        item = ShopCartItemFactory()
+        resp = self.client.post(
+            f"{BASE_URL}/{shopcart.id}/items",
+            json=item.serialize(),
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+        data = resp.get_json()
+        item_id = data["id"]
+
+        # add the second item
+        item_2 = ShopCartItemFactory()
+        resp = self.client.post(
+            f"{BASE_URL}/{shopcart.id}/items",
+            json=item_2.serialize(),
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+
+        # send delete request to delete the first item
+        resp = self.client.delete(
+            f"{BASE_URL}/{shopcart.id}/items/{item_id}",
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_204_NO_CONTENT)
+
+        resp = self.client.get(
+            f"{BASE_URL}/{shopcart.id}/items/{item_id}",
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_404_NOT_FOUND)
+
+        # the total price should equal to the second item's total price
+        resp = self.client.get(
+            f"{BASE_URL}/{shopcart.id}", content_type="application/json"
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        data = resp.get_json()
+        self.assertEqual(data["total_price"], str(item_2.price * item_2.quantity))
+
+    def test_shopcart_total_price_with_update_item(self):
+        """
+        It should update the shopcart total price
+        once an item is updated
+        """
+        # create a known item
+        shopcart = self._create_shopcarts(1)[0]
+        item = ShopCartItemFactory()
+        resp = self.client.post(
+            f"{BASE_URL}/{shopcart.id}/items",
+            json=item.serialize(),
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+
+        data = resp.get_json()
+        logging.debug(data)
+        item_id = data["id"]
+        data["quantity"] = 3
+
+        # send the update back
+        resp = self.client.put(
+            f"{BASE_URL}/{shopcart.id}/items/{item_id}",
+            json=data,
+            content_type="application/json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        # check total price
+        resp = self.client.get(
+            f"{BASE_URL}/{shopcart.id}", content_type="application/json"
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        data = resp.get_json()
+        self.assertEqual(data["total_price"], str(item.price * 3))