What Buy - Compare prices

Imagining that you're out shopping and see the same product in two different packages, one smaller and the other larger, how to know which left more account?
You open the application and puts their prices, then the app will tell you what makes up more, and what percentage of the difference between them.

Very useful to know which beer makes up more buying, smaller or larger cans. You simply put the price and the ML of the two to see the difference.