WordPress – How to manage different weight units at the product level in WooCommerce?

It is possible to add an additional field (radio buttons) in the admin product pages next to the weight field (on the shipping tab settings), to manage different weight units at the product level.

Here is the code:

// Add custom fields to product shipping tab
add_action( 'woocommerce_product_options_dimensions', 'add_product_weight_unit_option');
function add_product_weight_unit_option(){
    global $product_object;

    $weight_unit = $product_object->get_meta('_weight_unit');

    woocommerce_wp_radio(
        array(
            'id'          => '_weight_unit',
            'label'       => __( 'Weight unit', 'woocommerce' ),
            'options'     => array(
                'Kg'        => __( 'Kg (default)', 'woocommerce' ),
                'Litre'     => __( 'Litre', 'woocommerce' ),
                'Pound'     => _x( 'Pound', 'Tax status', 'woocommerce' ),
            ),
            'value'       => $weight_unit ? $weight_unit : 'Kg',
        )
    );
}

// Save custom fields to product shipping tab
add_action('woocommerce_admin_process_product_object', 'save_google_meet_link_custom_field');
function save_google_meet_link_custom_field( $product ) {
    if ( isset($_POST['_weight']) && ! empty($_POST['_weight']) && isset($_POST['_weight_unit']) ) {
        $product->update_meta_data( '_weight_unit', esc_attr($_POST['_weight_unit']) );
    } 
}

// Formating weight with the weight different weight ubits
add_filter( 'woocommerce_format_weight', 'custom_format_weight', 20, 2 );
function custom_format_weight( $weight_string, $weight ){
    $weight_string  = wc_format_localized_decimal( $weight );

    if ( ! empty( $weight_string ) ) {
        $weight_label = get_post_meta( get_the_ID(), '_weight_unit', true );

        $weight_string = sprintf(
            _nx( '%1$s  %2$s', '%1$s  %2$s'.'s', $weight, 'formatted weight', 'woocommerce' ),
            $weight_string,
            $weight_label ? $weight_label : get_option( 'woocommerce_weight_unit' ),
        );
    } else {
        $weight_string = __( 'N/A', 'woocommerce' );
    }

    return $weight_string;
}

Code goes in functions.php file of the active child theme (or active theme). Tested and works.