🌿 IBU Calculator (Tinseth)
Add your hop additions — weight, alpha-acid percentage and boil time — with your boil gravity and volume to get the total IBU.
| Hops (g) | Alpha acid % | Boil (min) | IBU | |
|---|---|---|---|---|
| 32.3 | ||||
| 8 |
Total bitterness
40.3 IBU
Uses Glenn Tinseth's utilization model: bitterness rises with boil time and falls as wort gravity increases (sugar suppresses hop utilization). Enter each hop addition's weight, alpha-acid percentage (from the packet) and boil time. Late/whirlpool/dry hops (0 min) add little measured IBU. Values are an estimate; actual bitterness varies with hop form, boil vigour and equipment. 🔒 In your browser.
How the ibu calculator (tinseth) works
Bitterness comes from alpha acids in the hops isomerising during the boil. The tool uses Glenn Tinseth's widely-used model: each addition contributes bitterness based on the alpha acids added (weight × alpha% ÷ volume) times a utilization factor that rises with boil time and falls as wort gravity increases. It sums every addition for the total IBU and shows each one's share.
IBU estimates are exactly that — estimates. The Tinseth model assumes a normal boil; hop form (pellets vs whole), boil vigour, a hop stand or whirlpool, and your equipment all shift real utilization. Late and dry-hop additions add lots of aroma but little measured IBU. Use it to compare and balance recipes rather than as an exact lab figure.
Frequently asked questions
How is IBU calculated?
IBU = utilization × the alpha acids added (in mg/L). Utilization comes from the Tinseth formula: it increases with boil time and decreases as wort gravity rises. Each hop addition is calculated separately and summed.
What is the Tinseth formula?
Glenn Tinseth's hop utilization model: utilization = bigness factor × boil-time factor, where bigness = 1.65 × 0.000125^(gravity−1) and boil-time factor = (1 − e^(−0.04 × minutes)) ÷ 4.15. It's the default in most brewing software.
Why does higher gravity lower the IBU?
A denser, sugarier wort extracts alpha acids less efficiently, so the same hops in a stronger beer give fewer IBU. That's the "bigness factor" — big beers need proportionally more hops to hit the same bitterness.
Do late and dry hops add IBU?
Very little measured IBU — bitterness needs boil time to isomerise the alpha acids. A 5-minute or flame-out addition contributes mostly flavour and aroma, and dry hops add aroma with essentially no IBU, though they can taste bitter.
How accurate is the IBU estimate?
It's a solid relative guide but not a lab measurement. Real utilization depends on hop form, boil vigour, whirlpool time and your system, so treat the number as a target for balancing a recipe rather than an exact value.