/* save variable product percentage single product page */
add_filter( 'woocommerce_variable_price_html', 'bbloomer_variation_price_format_310', 10, 2 );
function bbloomer_variation_price_format_310( $price, $product ) {
// Getting the clean numeric prices (without html and currency)
$min_var_reg_price = $product->get_variation_regular_price( 'min', true );
$min_var_sale_price = $product->get_variation_sale_price( 'min', true );

// Percentage calculation and text
$percentage = round( ( $min_var_reg_price - $min_var_sale_price ) / $min_var_reg_price * 100 ).'%';
$percentage_txt = ' -'.$percentage.'';

return '' . wc_price( $min_var_reg_price ) . ' ' . wc_price( $min_var_sale_price ) . $percentage_txt . '';
}