How do you then calculate the IBUs using BeerSmith?
Well...you don't.
Formulas are very flawed - let me show you why.
6 Gallon IPA Recipe
70% efficiency,
Rager for bitterness
15 lbs 2-row
1 lb C40
1 oz magnum @60
.5 oz Centennial @30
1 oz Centennial @10
1 oz Centennial @1
WLP001
7.1% ABV (good)
1.015 FG (good)
8 SRM (good)
89 IBU (too hoppy for style - IPA style range is 40-70)
Why change the recipe to fit the style when you can just change the bittering formula?
6 Gallon IPA Recipe
70% efficiency,
Tinseth for bitterness
15 lbs 2-row
1 lb C40
1 oz magnum @60
.5 oz Centennial @30
1 oz Centennial @10
1 oz Centennial @1
7.1% ABV (good)
1.015 FG (good)
8 SRM (good)
69 IBU (good)
Now my IPA is to style!
That rant is not very helpful, but it does make a point.
So to be more helpful (like I mentioned in an earlier post) if you want to use long hot whirlpools but still want to come up with some type of IBU number through a formula to speak in a language you are used to, enter your recipe into a program, then increase the minutes of each hop addition by the length of the whirlpool you are doing.
So if your recipe was:
1 oz at 60
.5 oz at 30
1 oz at 10
1 oz at 1
but you want to use a 30 minute whirlpool,
change the calculation to:
1 oz at 90
.5 oz at 60
1 oz at 40
1 oz at 11
You will see the bitterness calculation you typically use skyrocket, and honestly, if you brewed the
same recipe twice, once with chilling at zero, once with long hot whirlpool, you'll notice the effort with the long hot whirlpool will taste dramatically more bitter....no matter what the number on the recipe says. For that reason, I say that if you are going to employ a long hot whirlpool (hot being around 200F), roll back the quantities on those first couple additions, and just taste how much bitterness the long whirlpool gives you.