Sizes is a great app that helps you in resizing images for Retina display.
Just drop your files on the icon and... wait a second!
You don't need to name your files properly - Sizes does it for you. And of course you can change the image suffix. Really simple.
Changes in user interface.
Corrected error that crashes application at first start in OS X 10.9
With Family Sharing set up, up to six family members can use this app.