At some point in time either yourself or a client will be building a WooCommerce site any may want to display the total percentage saved on WooCommerce sale products. By default WooCommerce does not display the percentage the customer will save on a sale product but thanks to Gerhard Potgieter this is easily possible by using an a elegant little WooCommerce filter.
Below is a screenshot of how a standard unmodified WooCommerce on sale product displays, You will notice it’s recommended price has a strike through and the sales price is the visible one.