The EPA recently released a new food cost calculator that estimates the financial savings of source reduction, donation, and composting of food, and recycling of yellow grease. The calculator takes user input such as food costs and amounts of waste (so you will need some in-house data) and calculates savings and environmental benefits based on several scenarios. The calculator is created in a Microsoft Excel file and you will need macros enabled to run the file.
In addition to the calculator, the EPA also provides a wealth of information on food waste.
The food waste calculator is available on the EPA website.