Beersmith is very good at calculating IBU's.
It is one of the best programs for that bit brewing math.
Be sure to adjust for the AA of your Chinook hops !!!
that could make difference in your outcome.
I brew with Chinook hops often, you should get your desired result with out any real trouble, BUT!, let it age, it gets really good around 3-6 months !!!
I don't want to never stop having poop stickers. -Austin post #6909379
I say some stupid chit -TXCrash post #7247287