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IBU (Tinseth) Calculator

Estimate your beer's bitterness in IBU with the Tinseth method.

How it is calculated

The Tinseth utilisation is the product of a gravity factor and a time factor: bigness = 1.65 × 0.000125(OG − 1), time factor = (1 − e−0.04 × t) / 4.15 with t in minutes, and utilisation = bigness × time factor. Then IBU = utilisation × (AA/100 × oz × 7490 / gallons). Hop weight is in ounces, AA is alpha acid in percent, volume is in US gallons and OG is wort gravity as a specific gravity (1.050). The last bracket is the alpha acid added, in mg/L. Utilisation falls smoothly as gravity rises and is zero at zero minutes. The result shows IBU with one decimal plus the utilisation used. Alpha acid must be above 0 and at most 100, gravity must lie between 0.980 and 1.200, otherwise there is no result. It covers a single hop addition, so add multiple additions yourself.

Worked example

One ounce of 7 % alpha acid hops boiled 60 minutes in 5 gallons of 1.050 wort. Bigness = 1.65 × 0.0001250.05 ≈ 1.0528. Time factor = (1 − e−2.4) / 4.15 ≈ 0.2191. Utilisation = 1.0528 × 0.2191 ≈ 23.07%. Alpha acid added = 0.07 × 1 × 7490 / 5 = 104.9 mg/L, so IBU = 0.2307 × 104.9 ≈ 24.2. At OG 1.070 the same addition gives about 20.2 IBU.

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Common mistakes

  • Entering the hop weight in grams. The field is ounces, so a 28 g addition must be entered as 1; typing 28 gives about 677 IBU.
  • Entering the batch volume in litres instead of US gallons. A 19 L batch typed as 19 gives 6.4 IBU instead of 24.2, about 3.8 times too low.
  • Typing the gravity as 1050 or 50 instead of 1.050. Values outside 0.980–1.200 show no result.
  • Entering alpha acid as a fraction (0.07) instead of a percent (7). That gives 0.2 IBU, and using the alpha acid of a different hop variety or crop year than the one on the bag also skews the answer.
  • Reading an estimate of the whole recipe from one addition. Each hop addition has its own boil time and must be calculated and added up.

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.

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