I know there are probably some easy to find apps out there to calculate all this for me but I'm trying to learn/understand the math before I start making it easy. I just want to make sure I'm not doing the below calculations wrong. I left out 3.3 lbs of the 6.6 total LME until the last 5 minutes of the boil. Calculate Boil Gravity 1 lbs DME in 3 gal water = 1*40/3 = 13.3 3.3 lbs LME in 3 gal water = 3.3*36/3 = 39.6 = 1.053 Calculate AAUs 1 oz Cascade 60 min 7% Alpha = 7 AAUs 2 oz Columbus 30 min 15.6% Alpha = 31.2 AAUs 1.5 oz Cascade 0 min 7% Alpha = 10.5 AAUs Calculated IBUs 7*.231*75/5 = 24 31.2*.177*75/5 = 83 = 107 IBUs Thanks, Tim
There are various formulas used to estimate hop utilization (IBUs). Some of the popular ones are from Rager and Tinseth but there are others out there (e.g., Garetz, Ray Daniels, etc.). The value of 107 IBUs is consistent with the Glenn Tinseth estimation formula. This link may be of interest: http://www.rooftopbrew.net/ibu.php Cheers!
By my own calculations, I get 117 IBUs for 5 gallons, or 194 IBUs for 3 gallons if you didn't dilute down to 5 (you didn't say). In either case, your actual IBUs will probably hit the maximum possible amount of around 90 IBUs. If you can get more IBUs than that into the beer, humans can't taste more than 90 anyway.
Another quick question about calculating OG, do steeped grains add to the OG and if so what would the calculation for that be? This recipe is supposed to have a OG of 1.061-1.065 and I was right around 1.060. Calculating expected OG myself I was using (1*40/5)+(6.6*36/5) = 1.055 which is below theirs and the actual OG I was getting.
Steeped grains do indeed change the gravity. The calculation for grains is done the same way as for extract, although the constant you use instead of 40 or 36 is around 25, plus or minus a couple points. It will get you pretty close if you use 25.
