Rager IBU Calculator

This page provides a calculator for predicting IBUs using the Jackie Rager formula from an article in Zymurgy (vol. 13, no. 4, pp. 54-54, 1990). This formula is provided at Norm Pyle's Hops FAQ.

Inputs:

Input Units: metric or U.S. customary (e.g. gallons, ounces)

Wort:
Boil Time (minutes):
Evaporation Rate (G/hr):
Wort Volume (G): pre-boil or post-boil volume
(Post-Boil) Original Gravity:
Wort/Trub Left in Kettle (G): (only needed for partial boils)
(Partial Boil) Added Water (G):

Hops:
Number of Hop Additions:
Global IBU Scaling Factor:

Outputs:


Save and Load:

Save to File:
Load from File:

Note that the Rager utilization function is greater than zero even at a boil time of zero minutes. Jackie Rager may have observed the contribution to the IBU from oxidized alpha acids produced when hops are added to the kettle, and included this in his utilization function:

utilization


Versions:

1.0.0: (2021-Aug-21) Initial version.
1.0.1: (2021-Nov-25) Minor updates.

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Copyright © 2021 John-Paul Hosom, all rights reserved. While I hope that you find this page useful, I make no guarantees about the accuracy or suitability of the results. Predicting IBUs is a bit of a "black art", because there are so many variables and there is so much variability. The only way to really know the IBU level of a beer is to have it professionally tested, which is something I highly recommend. Cheers!