IBU Calculator

Calculate the bitterness (IBU) and alpha acid units of your hop additions with the Tinseth formula, in metric, US or imperial units.

MetricUSImperial (UK)

Batch volume (L)

Volume of finished beer, after the boil

Wort gravity (SG)

Average gravity of the wort during the boil

Hop addition 1

Hop amount (g)

Alpha acid (%)

Boil time (min)

23.1% utilization · 32.3 IBU · 9.9 AAU

Total bitterness32.3IBUAlpha acid units9.9AAU

Results are estimates provided "as is," for informational and planning purposes only, without warranties of any kind. Check them before you rely on them: you are responsible for decisions about your beer and equipment, including pressure and carbonation levels, the pressure ratings of your kegs and fittings, and any alcohol content you declare. Use of this calculator is subject to our Terms and Conditions.

Plan recipes and track every batch with these calculators built in. Foambyte is free to start.

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How IBUs are calculated

This calculator uses Glenn Tinseth’s formulas. Each hop addition adds alpha acids to the wort, and the boil turns part of them into bitter iso-alpha acids. The share that ends up in the beer is the hop utilization:

U = 1.65 \times 0.000125^{\,(G - 1)} \times \frac{1 - e^{-0.04\,t}}{4.15}

where $G$ is the average gravity during the boil and $t$ is the boil time in minutes.

The first part (the “bigness factor”) lowers utilization as the wort gets denser; the second part rises with boil time and levels off after about an hour. The bitterness of the addition is then:

\text{IBU} = \frac{\alpha \times m \times 1000}{V} \times U

where $\alpha$ is the alpha acid as a decimal (10% = 0.10), $m$ the hops in grams and $V$ the volume of finished beer in liters.

For example, 28 g of a 10% alpha acid hop boiled for 60 minutes in wort averaging 1.050, for 20 L of beer, has a utilization of 23.1% and adds about 32.3 IBU. The total bitterness of a recipe is the sum of its additions.

Inside Foambyte, IBUs are calculated as you build a recipe, together with the gravity, color and the rest of your brew-day numbers.

Reference table

Tinseth hop utilization (%) by boil time (rows) and average boil gravity (columns)
Minutes \ gravity	1.030	1.040	1.050	1.060	1.070	1.080	1.090	1.100
0 min	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
5 min	5.5	5.0	4.6	4.2	3.8	3.5	3.2	2.9
10 min	10.0	9.1	8.4	7.6	7.0	6.4	5.8	5.3
15 min	13.7	12.5	11.4	10.5	9.6	8.7	8.0	7.3
20 min	16.7	15.3	14.0	12.8	11.7	10.7	9.8	8.9
30 min	21.2	19.4	17.7	16.2	14.8	13.5	12.4	11.3
45 min	25.3	23.2	21.2	19.4	17.7	16.2	14.8	13.5
60 min	27.6	25.2	23.1	21.1	19.3	17.6	16.1	14.7
75 min	28.9	26.4	24.1	22.0	20.1	18.4	16.8	15.4
90 min	29.5	27.0	24.7	22.6	20.6	18.8	17.2	15.7

Sources

Glenn Tinseth. “Glenn's Hop Utilization Numbers”, The Real Beer Page. Hop utilization (bigness and boil time factors) and IBU formulas; archived copy, as the original page has been retired.

Frequently asked questions

What is an IBU?

An International Bitterness Unit corresponds to roughly one milligram of isomerized alpha acids per liter of beer. Most beers fall between about 10 and 100 IBU.

Why do late hop additions add so few IBU?

Alpha acids only become bitter once boiling isomerizes them, which takes time. A 60-minute addition reaches several times the utilization of a 10-minute addition, so late hops add mostly aroma and flavor.

Which gravity should I enter?

The average gravity of the wort during the boil. Higher gravity lowers hop utilization, so using the gravity of the finished wort slightly understates the IBU of a long boil with a lot of evaporation.

What are alpha acid units (AAU)?

Alpha acid units, also called homebrew bittering units (HBU), are the hop amount in ounces multiplied by the alpha acid percentage. One ounce of a 10% hop is 10 AAU. They describe the bittering potential of an addition regardless of batch size or boil time.

How accurate is the Tinseth formula?

It is an estimate fitted to Glenn Tinseth's measurements, and actual bitterness depends on your kettle, hop form and freshness, whirlpool time and fermentation. Additions with no boil time, such as dry hops, count as zero here. Tinseth suggests adjusting the formula's 4.15 factor if your measured utilization differs.