IBU (Tinseth) Calculator

About this calculator

The Tinseth formula, published by Glenn Tinseth in 1997 and still the most widely used hop-bitterness model in homebrewing, estimates International Bitterness Units (IBU) from the hop's alpha acid percentage, the weight of hops added, boil time, wort gravity and batch volume, combining a utilization curve — how much of the available alpha acid actually isomerizes into bitterness compounds — that rises with boil time and falls as wort gravity increases, since denser wort inhibits isomerization.

Homebrewers use IBU calculations when designing or scaling a recipe to hit a target bitterness for style — an IPA might target 40-70+ IBU while a light lager sits closer to 10-20 — and because utilization depends on boil time and gravity, the same hop addition contributes very different bitterness depending on when in the boil it's added and how strong the wort is at that point.

This calculator takes your alpha acid percentage, hop weight, boil time, wort gravity and batch volume, and returns the estimated IBU contribution using the Tinseth utilization model.