Reference

IBU by hop weight and alpha acid

Quick answer

Bitterness for a given hop charge, calculated by the Tinseth and Rager equations, which disagree by a predictable margin.

This section holds 27 worked pages. Every figure comes from the same formula library the calculators use, and each page states whether its numbers rest on a published standard or on brewing convention.

Every page below is worked out from the published equations in this site's formula library, not copied from another calculator. Where a figure rests on brewing convention rather than a published standard, the page says so on the row itself.


All 27 pages in this section


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Frequently asked questions

Why do Tinseth and Rager give different IBU?
They are two different published models of hop utilisation, fitted to different data. Rager generally returns a higher figure than Tinseth for the same hop charge, often by around a third at full boil times. Neither is the true value, because calculated IBU is a model rather than a measurement. Stay with one model so your recipes remain comparable.
Does calculated IBU match measured bitterness?
Not reliably. Calculated IBU predicts how much isomerised alpha acid should end up in the beer, while a laboratory IBU measures what actually did. Heavily dry hopped beers are the clearest case, where perceived bitterness can rise noticeably without the measured number moving much.

Researched from published brewing formulas, manufacturer specifications and verified owner reviews. This is general guidance, not professional advice.