diff --git a/config/schema/commerce_shipping.schema.yml b/config/schema/commerce_shipping.schema.yml
index e2c7e5d..70ad4d7 100644
--- a/config/schema/commerce_shipping.schema.yml
+++ b/config/schema/commerce_shipping.schema.yml
@@ -80,6 +80,22 @@ commerce_shipping.commerce_shipping_method.plugin.flat_rate_per_item:
       type: field.value.commerce_price
       label: 'Rate amount'
 
+commerce_shipping.commerce_shipping_method.plugin.flat_rate_plus_per_item:
+  type: commerce_shipping_method_configuration
+  mapping:
+    rate_label:
+      type: label
+      label: 'Rate label'
+    rate_description:
+      type: label
+      label: 'Rate description'
+    rate_amount:
+      type: field.value.commerce_price
+      label: 'Rate amount'
+    per_item_amount:
+      type: field.value.commerce_price
+      label: 'Per item amount'
+
 commerce_shipping_method_configuration:
   type: mapping
   mapping:
diff --git a/src/Plugin/Commerce/ShippingMethod/FlatRatePlusPerItem.php b/src/Plugin/Commerce/ShippingMethod/FlatRatePlusPerItem.php
new file mode 100644
index 0000000..8bc40ea
--- /dev/null
+++ b/src/Plugin/Commerce/ShippingMethod/FlatRatePlusPerItem.php
@@ -0,0 +1,81 @@
+<?php
+
+namespace Drupal\commerce_shipping\Plugin\Commerce\ShippingMethod;
+
+use Drupal\commerce_price\Price;
+use Drupal\commerce_shipping\Entity\ShipmentInterface;
+use Drupal\commerce_shipping\ShippingRate;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Provides the FlatRatePlusPerItem shipping method.
+ *
+ * @CommerceShippingMethod(
+ *   id = "flat_rate_plus_per_item",
+ *   label = @Translation("Flat rate + per item"),
+ * )
+ */
+class FlatRatePlusPerItem extends FlatRate {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    return [
+      'per_item_amount' => '',
+    ] + parent::defaultConfiguration();
+ }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildConfigurationForm($form, $form_state);
+
+    $per_item_amount = $this->configuration['per_item_amount'] ?: NULL;
+    // A bug in the plugin_select form element causes amount to be incomplete.
+    if (isset($per_item_amount) && !isset($per_item_amount['number'], $per_item_amount['currency_code'])) {
+      $per_item_amount = NULL;
+    }
+
+    $form['per_item_amount'] = [
+      '#type' => 'commerce_price',
+      '#title' => $this->t('Per item amount'),
+      '#description' => $this->t('Charged for each quantity of each shipment item.'),
+      '#default_value' => $per_item_amount,
+      '#required' => TRUE,
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+    parent::submitConfigurationForm($form, $form_state);
+    if (!$form_state->getErrors()) {
+      $values = $form_state->getValue($form['#parents']);
+      $this->configuration['per_item_amount'] = $values['per_item_amount'];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function calculateRates(ShipmentInterface $shipment) {
+    $amount = Price::fromArray($this->configuration['rate_amount']);
+    $per_item_amount = Price::fromArray($this->configuration['per_item_amount']);
+    $quantity = $shipment->getTotalQuantity();
+
+    $rates = [];
+    $rates[] = new ShippingRate([
+      'shipping_method_id' => $this->parentEntity->id(),
+      'service' => $this->services['default'],
+      'amount' => $amount->add($per_item_amount->multiply($quantity)),
+    ]);
+
+    return $rates;
+  }
+
+}
diff --git a/tests/src/FunctionalJavascript/CartIntegrationTest.php b/tests/src/FunctionalJavascript/CartIntegrationTest.php
index 08213f8..e2a36da 100644
--- a/tests/src/FunctionalJavascript/CartIntegrationTest.php
+++ b/tests/src/FunctionalJavascript/CartIntegrationTest.php
@@ -217,6 +217,97 @@ class CartIntegrationTest extends CommerceWebDriverTestBase {
 
   }
 
+  /**
+   * Test for Flat Rate + Per Item shipping cost updates.
+   */
+  public function testRecalculatePlusPerItem() {
+    // Create a flat rate + per item.
+    $this->createEntity('commerce_shipping_method', [
+      'name' => 'Flat Rate + Per Item',
+      'stores' => [$this->store->id()],
+      'plugin' => [
+        'target_plugin_id' => 'flat_rate_plus_per_item',
+        'target_plugin_configuration' => [
+          'rate_label' => 'Flat Rate + Per Item',
+          'rate_amount' => [
+            'number' => '9.00',
+            'currency_code' => 'USD',
+          ],
+          'per_item_amount' => [
+            'number' => '3.00',
+            'currency_code' => 'USD',
+          ],
+        ],
+      ],
+      'conditions' => [
+        [
+          'target_plugin_id' => 'shipment_quantity',
+          'target_plugin_configuration' => [
+            'operator' => '>',
+            'quantity' => '1',
+          ],
+        ],
+      ],
+    ]);
+
+    // Add product to order and calculate shipping.
+    $this->drupalGet($this->firstProduct->toUrl()->toString());
+    $this->submitForm([], 'Add to cart');
+    $this->drupalGet('checkout/1');
+    $address = [
+      'given_name' => 'John',
+      'family_name' => 'Smith',
+      'address_line1' => '1098 Alta Ave',
+      'locality' => 'Mountain View',
+      'administrative_area' => 'CA',
+      'postal_code' => '94043',
+    ];
+    $address_prefix = 'shipping_information[shipping_profile][address][0][address]';
+    $this->getSession()->getPage()->fillField($address_prefix. '[country_code]', 'US');
+    foreach ($address as $property => $value) {
+      $this->getSession()->getPage()->fillField($address_prefix . '[' . $property . ']', $value);
+    }
+
+    $this->getSession()->getPage()->findButton('Recalculate shipping')->click();
+    $this->assertSession()->assertWaitOnAjaxRequest();
+    $this->getSession()->getPage()->uncheckField('payment_information[add_payment_method][billing_information][copy_fields][enable]');
+    $this->assertSession()->assertWaitOnAjaxRequest();
+    $this->submitForm([
+      'payment_information[add_payment_method][payment_details][number]' => '4111111111111111',
+      'payment_information[add_payment_method][payment_details][expiration][month]' => '02',
+      'payment_information[add_payment_method][payment_details][expiration][year]' => $this->getCardExpirationYear(),
+      'payment_information[add_payment_method][payment_details][security_code]' => '123',
+      'payment_information[add_payment_method][billing_information][address][0][address][given_name]' => 'Johnny',
+      'payment_information[add_payment_method][billing_information][address][0][address][family_name]' => 'Appleseed',
+      'payment_information[add_payment_method][billing_information][address][0][address][address_line1]' => '123 New York Drive',
+      'payment_information[add_payment_method][billing_information][address][0][address][locality]' => 'New York City',
+      'payment_information[add_payment_method][billing_information][address][0][address][administrative_area]' => 'NY',
+      'payment_information[add_payment_method][billing_information][address][0][address][postal_code]' => '10001',
+    ], 'Continue to review');
+
+    $this->assertSession()->pageTextContains('Shipping $10.00');
+
+    // Test whether the shipping amount gets updated.
+    $this->drupalGet('/cart');
+    $this->getSession()->getPage()->fillField('edit_quantity[0]', '3');
+    $this->getSession()->getPage()->findButton('Update cart')->click();
+    $this->assertSession()->pageTextContains('Shipping $30.00');
+
+    // Switch to "Flat Rate + Per Item" and recalculate shipping.
+    $this->drupalGet('checkout/1');
+    $this->getSession()->getPage()->findButton('Recalculate shipping')->click();
+    $this->assertSession()->assertWaitOnAjaxRequest();
+    $this->getSession()->getPage()->findField('Flat Rate + Per Item: $18.00')->click();
+    $this->assertSession()->assertWaitOnAjaxRequest();
+    $this->assertTrue($this->getSession()->getPage()->findField('Flat Rate + Per Item: $18.00')->isChecked());
+
+    $this->submitForm([], 'Continue to review');
+    $this->assertSession()->pageTextContains('Shipping method');
+    $this->assertSession()->pageTextNotContains('Flat Rate Per Item');
+    $this->assertSession()->pageTextContains('Flat Rate + Per Item');
+    $this->assertSession()->pageTextContains('Shipping $18.00');
+  }
+
   /**
    * Test for recalculating shipping trough cart/checkout steps.
    */