[nvshooter2276]

Planning on adding a can of brewdemon Wild Spirit IPA (one gallon) to a can of mr. beer Diablo IPA (two gallons) and fermenting it in at least 3.5 gallons of filtered water. How would I calculate the combined IPA ratings of these two syrups? At this point in time, I have no idea what is the IBU of either. Would I average the total IBU ratings of the two?

[Richard]

I think the correct thing to do would be to do a weighted average, based on the relative amounts of each. If you have 1 gallon of beer with IBU = A and 2 gallons of beer with IBU B then mixing them would give IBU = (1*A + 2*B)/3. If you take that and add it to 3.5 gallons of water with IBU = 0, then the result would be IBU=(1*A +2*B+3.5*0)/6.5

That is the math behind it, but how your beer tastes depends on a lot of other factors.

[nvshooter2276]

I can see your reasoning. The IBU of the one-gallon Wild Spirit IPA is 58, as mixed according to the directions. Haven't done any research as to what is the IBU of the two-gallon Diablo IPA. I have no idea as to when I'll ever get to proceed with this brew. I work a lot, and there's always something to consume my time when I'm not at work.

I have three cans of mr. beer's American Porter LME, to make six gallons. What would a beer made with all three cans-- but with just five gallons of water-- taste like? Too sweet? Too bitter? A ton of mouthfeel? Too much Porter flavor? Sticky and cloying? I'm averse to using half a can of the LME because then I'll have an open can that may not be used for months and months. Maybe I can freeze it to keep it unadulterated by the stuff that floats around in my Northern Nevada air?

[nvshooter2276]

IBU of Wild Spirit LME is 58 as a one-gallon brew. It's 70 for the Diablo as a two-gallon brew. Per your equation, I get (58 + 140)/3 = 66 IBU. I do not understand your use of the asterisk in your equation. Am I supposed to double the 70 IBU of the Diablo (as I show as 140)? Even if I have made a mistake in my calculation, just believing I'm drinking a beer of 66 IBU is good enough.

[Richard]

The asterisk means multiplication, a common convention in many computer programming languages. You did it correctly.