WARNING! The Recipator calculator is crap! I tried using it one time...plugged in 10 ounces, TEN FREAKIN OUNCES, of hops, including high AA hops, and the stupid thing claimed that my IBU would be 45.
Stay away from that site's calculator (though, the recipe database is cool). If you want, you can go to promash.com and download the free trial. Sure, you can only save/edit a couple times, but if all you're looking for is a calculator, the demo works great.