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Brews & Views Bulletin Board Service * Brews and Views Archive 2011 * Archive through December 10, 2011 * IBU calcs and the number 1.34 < Previous Next >

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mark taylor
Intermediate Member
Username: Marktaylo

Post Number: 391
Registered: 06-2003
Posted From: 71.146.68.17
Posted on Monday, October 03, 2011 - 04:34 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Can anyone tell me where this number (1.34)comes from? In doing the calculation for determining IBU's I use a fomula that is the (hop qty in oz. x AA% x utilization %) devided by (gals. x 1.34)
The 1.34 is a fixed number but what is it based on? Thanks
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 13273
Registered: 01-2002
Posted From: 24.150.49.181
Posted on Monday, October 03, 2011 - 05:07 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

The IBU is by definition a metric measurement (milligrams/liter of dissolved iso-alpha acid. The 1.34 factor converts the utilization percentage to a decimal figure, ounces of weight to milligrams, and gallons of volume to liters.
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 7846
Registered: 03-2004
Posted From: 208.102.247.68
Posted on Monday, October 03, 2011 - 05:58 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I use a simplified formula that can be performed in your head.

IBU = oz. * AA * 20 / gal.

For five gallon batches is even simpler.

IBU = oz. * AA * 4

This assumes a 60 minute boil. Scale the constant for shorter additions.

No, it is not perfect, but for most uses, it is very close.
 

mark taylor
Intermediate Member
Username: Marktaylo

Post Number: 392
Registered: 06-2003
Posted From: 71.146.68.17
Posted on Monday, October 03, 2011 - 09:30 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks guys.

mark
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