diff --git a/src/Shipment.php b/src/Shipment.php
index 022a7643..714792ec 100644
--- a/src/Shipment.php
+++ b/src/Shipment.php
@@ -644,8 +644,8 @@ public function get_item_weights() {
 		if ( is_null( $this->weights ) ) {
 			$this->weights = array();
 
-			foreach ( $this->get_items() as $item ) {
-				$this->weights[ $item->get_id() ] = ( ( $item->get_weight() === '' ? 0 : $item->get_weight() ) * $item->get_quantity() );
+			foreach ( $this->get_items() as $k => $item ) {
+				$this->weights[ $k ] = ( ( $item->get_weight() === '' ? 0 : $item->get_weight() ) * $item->get_quantity() );
 			}
 
 			if ( empty( $this->weights ) ) {
@@ -665,8 +665,8 @@ public function get_item_lengths() {
 		if ( is_null( $this->lengths ) ) {
 			$this->lengths = array();
 
-			foreach ( $this->get_items() as $item ) {
-				$this->lengths[ $item->get_id() ] = $item->get_length() === '' ? 0 : $item->get_length();
+			foreach ( $this->get_items() as $k => $item ) {
+				$this->lengths[ $k ] = $item->get_length() === '' ? 0 : $item->get_length();
 			}
 
 			if ( empty( $this->lengths ) ) {
@@ -681,11 +681,11 @@ public function get_item_volumes() {
 		if ( is_null( $this->volumes ) ) {
 			$this->volumes = array();
 
-			foreach ( $this->get_items() as $item ) {
+			foreach ( $this->get_items() as $k => $item ) {
 				$dimensions = $item->get_dimensions();
 				$volume     = ( '' !== $dimensions['length'] ? (float) $dimensions['length'] : 0 ) * ( '' !== $dimensions['width'] ? (float) $dimensions['width'] : 0 ) * ( '' !== $dimensions['height'] ? (float) $dimensions['height'] : 0 );
 
-				$this->volumes[ $item->get_id() ] = $volume * (float) $item->get_quantity();
+				$this->volumes[ $k ] = $volume * (float) $item->get_quantity();
 			}
 
 			if ( empty( $this->volumes ) ) {
@@ -705,8 +705,8 @@ public function get_item_widths() {
 		if ( is_null( $this->widths ) ) {
 			$this->widths = array();
 
-			foreach ( $this->get_items() as $item ) {
-				$this->widths[ $item->get_id() ] = $item->get_width() === '' ? 0 : $item->get_width();
+			foreach ( $this->get_items() as $k => $item ) {
+				$this->widths[ $k ] = $item->get_width() === '' ? 0 : $item->get_width();
 			}
 
 			if ( empty( $this->widths ) ) {
@@ -726,8 +726,8 @@ public function get_item_heights() {
 		if ( is_null( $this->heights ) ) {
 			$this->heights = array();
 
-			foreach ( $this->get_items() as $item ) {
-				$this->heights[ $item->get_id() ] = ( $item->get_height() === '' ? 0 : $item->get_height() ) * $item->get_quantity();
+			foreach ( $this->get_items() as $k => $item ) {
+				$this->heights[ $k ] = ( $item->get_height() === '' ? 0 : $item->get_height() ) * $item->get_quantity();
 			}
 
 			if ( empty( $this->heights ) ) {
@@ -2291,7 +2291,7 @@ public function add_item( $item ) {
 	/**
 	 * Reset item content data.
 	 */
-	protected function reset_content_data() {
+	public function reset_content_data() {
 		$this->weights = null;
 		$this->lengths = null;
 		$this->widths  = null;
diff --git a/src/ShipmentItem.php b/src/ShipmentItem.php
index d46bfb27..5a66a2f8 100644
--- a/src/ShipmentItem.php
+++ b/src/ShipmentItem.php
@@ -668,6 +668,10 @@ public function set_sku( $sku ) {
 	 */
 	public function set_weight( $weight ) {
 		$this->set_prop( 'weight', '' === $weight ? '' : wc_format_decimal( $weight ) );
+
+		if ( $shipment = $this->get_shipment() ) {
+			$shipment->reset_content_data();
+		}
 	}
 
 	/**
@@ -677,6 +681,10 @@ public function set_weight( $weight ) {
 	 */
 	public function set_width( $width ) {
 		$this->set_prop( 'width', '' === $width ? '' : wc_format_decimal( $width ) );
+
+		if ( $shipment = $this->get_shipment() ) {
+			$shipment->reset_content_data();
+		}
 	}
 
 	/**
@@ -686,6 +694,10 @@ public function set_width( $width ) {
 	 */
 	public function set_length( $length ) {
 		$this->set_prop( 'length', '' === $length ? '' : wc_format_decimal( $length ) );
+
+		if ( $shipment = $this->get_shipment() ) {
+			$shipment->reset_content_data();
+		}
 	}
 
 	/**
@@ -695,6 +707,10 @@ public function set_length( $length ) {
 	 */
 	public function set_height( $height ) {
 		$this->set_prop( 'height', '' === $height ? '' : wc_format_decimal( $height ) );
+
+		if ( $shipment = $this->get_shipment() ) {
+			$shipment->reset_content_data();
+		}
 	}
 
 	public function get_dimensions( $context = 'view' ) {
@@ -707,6 +723,10 @@ public function get_dimensions( $context = 'view' ) {
 
 	public function set_quantity( $quantity ) {
 		$this->set_prop( 'quantity', absint( $quantity ) );
+
+		if ( $shipment = $this->get_shipment() ) {
+			$shipment->reset_content_data();
+		}
 	}
 
 	public function set_name( $name ) {
diff --git a/tests/unit-tests/shipment.php b/tests/unit-tests/shipment.php
index ef5188a7..659afdce 100644
--- a/tests/unit-tests/shipment.php
+++ b/tests/unit-tests/shipment.php
@@ -28,6 +28,29 @@ function test_shipment_weight() {
 		$this->assertEquals( 25, $shipment->get_total_weight() );
 	}
 
+	function test_shipment_content_weight() {
+		$shipment = new \Vendidero\Germanized\Shipments\SimpleShipment();
+
+		$item = new \Vendidero\Germanized\Shipments\ShipmentItem();
+		$item->set_weight( 1.5 );
+
+		$item_2 = new \Vendidero\Germanized\Shipments\ShipmentItem();
+		$item_2->set_quantity( 3 );
+		$item_2->set_weight( 5 );
+
+		$shipment->add_item( $item );
+		$shipment->add_item( $item_2 );
+
+		$this->assertEquals( 16.5, $shipment->get_content_weight() );
+
+		$item_2->set_quantity( 2 );
+		$this->assertEquals( 11.5, $shipment->get_content_weight() );
+
+		$item_2->set_quantity( 3 );
+		$item_2->set_weight( 3 );
+		$this->assertEquals( 10.5, $shipment->get_content_weight() );
+	}
+
 	function test_sync_shipment() {
 		$shipment = ShipmentHelper::create_simple_shipment();
 		$shipment->set_packaging_id( 0 );