IBU Calculator (Tinseth)
Bitterness in IBU from your hop additions by Glenn Tinseth’s formula: amount, alpha acid and boil time, with batch volume and boil gravity.
Each addition’s utilization and IBU, the total bitterness, and the bigness factor for your boil gravity — in ounces or grams, gallons or litres, with Tinseth’s calibration constant adjustable.
Example: 5.5 gal at 1.050 with 1 oz of 12 % hops at 60 minutes and 0.5 oz of 5.5 % at 15: 37.7 + 4.3 = 42 IBU; a flame-out addition counts 0.
Time in the boil,
strength of the wort.
How Tinseth’s formula turns alpha acids into IBU, what the two factors do, and what it leaves out.
Alpha acids added
Hops bitter beer through alpha acids that isomerize in the boil. The alpha acid added is its percentage × the hop weight, spread over the batch: milligrams per litre = alpha % × grams × 1000 ÷ litres.
Utilization
Tinseth’s utilization is a bigness factor, 1.65 × 0.000125^(boil gravity − 1), which falls as the wort gets stronger, times a boil-time factor, (1 − e^(−0.04 × minutes)) ÷ 4.15, which rises with time and levels off after about an hour. IBU is utilization × milligrams per litre.
Calibration
Tinseth described 4.15 as the number to adjust so the formula matches a brewer’s own system, so it is an input. Use the gravity of the wort in the boil, and the volume the bitterness ends up in.
What the estimate does not settle
Flame-out, whirlpool and dry hops get no bitterness in the formula but add some in practice; pellet versus whole hops and the hops’ age change utilization too. It is an estimate, not a lab IBU measurement. Inputs stay in your browser; the same anonymous usage counts as the rest of the site apply.
SOURCES
- Glenn Tinseth, “Glenn’s Hop Utilization Numbers” (1997) — the Tinseth formula
Last reviewed 24 September 2026. How results are checked: How we verify.