"WooCommerce Smart Sale Badge" enhances the built-in sale badge by displaying the total saving amount a customer will receive. The plugin works with all the WooCommerce product types – simple and external products will display a badge that says 'Save $X!', while variable and grouped products will display 'Save up to $X!'.
If you would like a more fully featured sale badge enhancement extension then be sure to check out Sale Flash Pro available for purchase from the WooThemes website: http://www.woothemes.com/products/sale-flash-pro/ (Sale Flash Pro was not written by me, but because WooCommerce Smart Sale Badge contains a limited feature set of Sale Flash Pro I will not be adding further features to this plugin).
Usage
Simply install and activate the plugin and you'll be good to go.