IBU Calculator — Tinseth Hop Bitterness Estimator
Free IBU calculator using the Tinseth formula. Add up to 3 hop additions for total and per-addition IBUs. American IPAs run 40-70 IBU.
IBU — International Bitterness Units — measures the concentration of iso-alpha acids in finished beer, where 1 IBU equals roughly 1 milligram of iso-alpha acids per liter. The calculator above uses the Tinseth formula, the model built into most brewing software, to estimate total and per-addition IBUs from up to three hop charges. Enter each addition’s weight, alpha acid percentage, and boil time, plus your batch volume and boil gravity, and it returns the bitterness each charge contributes and the sum. A 1-ounce charge of 10% alpha hops boiled 60 minutes in 5 gallons at 1.050 gravity lands near 35 IBU. Because bitterness depends on boil time, gravity, and volume together, small recipe changes shift the result more than most brewers expect. This page explains what the formula does, why a 60-minute addition dominates your bitterness, and why Tinseth, Rager, and Garetz calculators can disagree by 10-20% on the same recipe.
How are IBUs calculated?
IBUs are calculated by multiplying the milligrams per liter of added alpha acids by a utilization factor. In the Tinseth formula, IBU = (alpha acid decimal × grams of hops × 1000 ÷ liters) × utilization, where utilization = bigness factor × boil-time factor. The bigness factor is 1.65 × 0.000125^(gravity − 1), and the boil-time factor is (1 − e^(−0.04 × minutes)) ÷ 4.15. Sum every addition for your total IBU.
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IBU Calculator (Tinseth)
Key Information
| Parameter | Details |
|---|---|
| Tinseth utilization | bigness factor × boil-time factor |
| Bigness factor | 1.65 × 0.000125^(gravity − 1) |
| Boil-time factor | (1 − e^(−0.04 × minutes)) ÷ 4.15 |
| American IPA range | 40-70 IBU (BJCP 2021) |
Frequently Asked Questions
How are IBUs calculated?
IBUs are calculated by multiplying the milligrams per liter of added alpha acids by a utilization factor. In the Tinseth formula, IBU = (alpha acid decimal × grams of hops × 1000 ÷ liters) × utilization, where utilization = bigness factor × boil-time factor. The bigness factor is 1.65 × 0.000125^(gravity − 1), and the boil-time factor is (1 − e^(−0.04 × minutes)) ÷ 4.15. Sum every addition for your total IBU.
What is a good IBU for beer?
A good IBU depends entirely on style: American light lagers sit at 8-12 IBU, pilsners run about 25-45 IBU, American IPAs land at 40-70 IBU, and double IPAs reach 60-100 or more. Bitterness is best judged against malt using the BU:GU ratio; around 0.5 tastes balanced, while hop-forward IPAs push 0.7 to 0.9. Above roughly 100 IBU, added bitterness largely stops registering on the palate.
Do dry hops add IBU?
Dry hops add essentially zero IBU in the Tinseth formula because no boiling occurs, so no alpha acids isomerize. They still increase perceived bitterness through humulinones, oxidized alpha acids that bitter at about two-thirds the potency of iso-alpha acids per milligram. This is why a heavily dry-hopped hazy IPA can taste bitter while its calculated IBU stays near 40. Lab IBU tests also read dry-hopped beers inconsistently.
Are these calculators free to use?
Yes, all calculators on CalcCorp are completely free — no registration, no login, no hidden charges. Results are calculated instantly in your browser and we do not store any of your data.
How accurate are these calculations?
Our calculators use standard financial formulas updated with the latest tax rates, interest rates, and government policies for 2026. Results are accurate for planning purposes but should be verified with a professional for final decisions.
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Last updated: March 2026