How to calculate IBU?

Does anyone know an easy formula or way to calculate IBU? Depending on hops used, time boiled, and volume of your batch everything would change. There may be other variables that I am missing as well. Is there a formula that has those variables and then I can just put in the correct numbers?

Also, I'm not sure what a high number is on the IBU scale. I like IPAs so high is generally good. I've had Hop Devil and I consider that a perfect bitterness. Has anyone had this and do you know what that would rate on the IBU scale?

Thanks

I use BeerSmith for all my recipes, and it does all the calculations for me, to a high degree of accuracy. I'm not sure if there is an easy formula, but I'm sure there's some way to calculate it. Others have posted spreadsheets that do various other calculations for beer, so you might find one on here if your do a search. Alternately, someone started a thread with a huge list of homebrewing links; there could be one on that list.

IMO, a high IBU would be 40 or more. Anything less is still relatively drinkable for the average person. Once you get beyond 40, it's pretty noticeable. I think the highest commercial beers hit 120 IBUs, but I could be wrong. I think that 120 IBU is supposedly the most bitterness the human tongue can even taste; beyond is just bragging rights.

There are formulas in Ray Daniels' book Designing Great Beers. I summed up the IBU and the grain bill formulas in this thread.

- magno