I just downloaded BeerSmith 3 for iPad and started entering recipes for small 2 gallon batches using Mr Beer HMEs as published in the add-on. Once I got the equipment profile and batch size more or less dialed in, I found the IBU calculations were WAY OFF.
After some analysis, it looks like BeerSmith assumes a 1 lb can size and extrapolates the IBU of the extract accordingly to get their gal/lb IBU number. The only solution for me at this point was to do the math and plug the right number in. I took the Mr Beer published IBU number, multiplied it by gallon batch size (2 in this case) and divided it by can weight of 1.87lbs. I plugged that number in, and BeerSmith happily gives me the correct numbers now.
After some analysis, it looks like BeerSmith assumes a 1 lb can size and extrapolates the IBU of the extract accordingly to get their gal/lb IBU number. The only solution for me at this point was to do the math and plug the right number in. I took the Mr Beer published IBU number, multiplied it by gallon batch size (2 in this case) and divided it by can weight of 1.87lbs. I plugged that number in, and BeerSmith happily gives me the correct numbers now.