IBU Bitterness Calculator
Calculate hop bitterness in IBU (International Bitterness Units) using the Tinseth formula.
Enter hop weight, alpha acid, and boil time.
Estimated Bitterness (IBU)
How IBUs (International Bitterness Units) Are Calculated
IBU measures the bitterness of beer from hop alpha acids isomerized during the boil. The most widely used formula in homebrewing is Tinseth’s Formula.
Tinseth IBU Formula:
IBU = (AA% / 100) × Hops(g) × Utilization × 1000 / Volume(L)
Utilization depends on boil time and wort gravity:
Utilization = Bigness × Boil Time Factor
- Bigness = 1.65 × 0.000125^(gravity − 1)
- Boil Time Factor = (1 − e^(−0.04 × minutes)) / 4.15
Worked Example: 28g of Cascade hops (6% AA), 60-minute boil, 20-liter batch, OG 1.050:
- Bigness = 1.65 × 0.000125^0.050 ≈ 0.937
- Boil Time Factor = (1 − e^(−2.4)) / 4.15 ≈ (1 − 0.091) / 4.15 ≈ 0.219
- Utilization = 0.937 × 0.219 ≈ 0.205
- IBU = (6/100) × 28 × 0.205 × 1000 / 20 = 17.2 IBU
IBU Style Reference:
- American Lager: 5–15 IBU
- Pale Ale: 30–50 IBU
- IPA: 40–70 IBU
- Double IPA: 65–100 IBU
- Imperial Stout: 50–90 IBU
Key Variables:
- Higher alpha acid hops = more bitterness per gram
- Longer boil = higher utilization
- Higher gravity wort = lower utilization (sugar inhibits isomerization)
- Pellet hops: ~10% more efficient than whole leaf hops