Beer Forum

Posted: **Sat Feb 19, 2011 10:56 pm**

I went to LHBS today and got ingredients to brew Janet's brown tomorrow. I wasn't paying attention at the time but I got 3 ounces of Northern Brewer hops at 9.8% AA. The recipe calls for (in different additions, 3 oz) 6.5% AA. I understand how homebrew bittering units work, but I don't understand how to calculate IBUs. Is there a simple formula that I can use? Sorry to make it urgent, but my starter started rolling about 9 hours ago.

Posted: **Sun Feb 20, 2011 1:18 am**

http://realbeer.com/hops/FAQ.html

W = weight in oz
AA = Alpha Acid Percent (ie, 4% means use 0.04)
UTIL = Utilization - 60 mins -> .28, 15 mins -> .08, -0 mins - 0
V = volume in gallons

For FWH, use .10 (same as 20 min addition)

IBUs == Sum of (W * AA * UTIL * 7462) / (V * (1+GA))

If Gravity > 1.050
GA = (BOIL_GRAVITY - 1.050)
----------------------
0.2
otherwise,
GA = 0

Examples:
5 gallons 1.050 Weizen wort
1 oz 4% Hallertaur at 60 mins
GA = (1.050 â€“ 1.050)/0.2 = 0
(1 * .04 * .28 * 7462) / (5) == 16.71 IBUs Total

5 gallons 1.065 IPA wort
1oz Cascade @60
2 oz Cascade@15
2 oz Cascade@flameout
GA = (1.065 â€“ 1.050)/0.2 = .075
(1 * .08 * .28 * 7462) / (5 * 1.075) = 31.09
(2 * .08 * .08 * 7462) / ( 5 * 1.075) = 17.76 ==
31.09 + 17.76 = 48.85 IBUs total

Hope this helps

Posted: **Sun Feb 20, 2011 3:32 am**

it does,thank you muchos

Posted: **Sun Feb 20, 2011 6:17 am**

BDawg wrote:http://realbeer.com/hops/FAQ.html

W = weight in oz
AA = Alpha Acid Percent (ie, 4% means use 0.04)
UTIL = Utilization - 60 mins -> .28, 15 mins -> .08, -0 mins - 0
V = volume in gallons

For FWH, use .10 (same as 20 min addition)

IBUs == Sum of (W * AA * UTIL * 7462) / (V * (1+GA))

If Gravity > 1.050
GA = (BOIL_GRAVITY - 1.050)
----------------------
0.2
otherwise,
GA = 0

Examples:
5 gallons 1.050 Weizen wort
1 oz 4% Hallertaur at 60 mins
GA = (1.050 â€“ 1.050)/0.2 = 0
(1 * .04 * .28 * 7462) / (5) == 16.71 IBUs Total

5 gallons 1.065 IPA wort
1oz Cascade @60
2 oz Cascade@15
2 oz Cascade@flameout
GA = (1.065 â€“ 1.050)/0.2 = .075
(1 * .08 * .28 * 7462) / (5 * 1.075) = 31.09
(2 * .08 * .08 * 7462) / ( 5 * 1.075) = 17.76 ==
31.09 + 17.76 = 48.85 IBUs total

Hope this helps

This is exactly why I use BeerSmith. My head hurts. :asshat:

Posted: **Sun Feb 20, 2011 1:08 pm**

+1 for computers....

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