WooCommerce Was, Now, Save % price

functions.php

<?php
// Add Now: R12, Was: R15, Save 20% price for items on sale
add_action( 'woocommerce_sale_price_html', 'wc_custom_sale_price', 10, 2 );
function wc_custom_sale_price( $price, $product ) {
	$percentage = round( ( ( $product->regular_price - $product->get_price() ) / $product->regular_price ) * 100 );
	return sprintf( __( 'Now: %s, Was: %s, Save %s', 'woocommerce' ), woocommerce_price( $product->get_price() ), woocommerce_price( $product->regular_price ), $percentage . '%' );
}
?>