Beer IBU Calculator
International Bitterness Units (IBU) quantify the bitterness in beer from isomerized alpha acids extracted from hops during the boil. Knowing the IBU of your homebrew is essential for recipe design, style compliance, and achieving balanced beer. The Tinseth formula is the industry standard for homebrewing IBU calculations, accounting for boil time, wort gravity, hop weight, and alpha acid percentage. This calculator supports multiple hop additions per batch. Enter the details for each hop addition below to get your total estimated IBU.
Tinseth IBU formula
Bigness factor = 1.65 * 0.000125^(wort_gravity - 1)
Boil time factor = (1 - e^(-0.04 * boil_minutes)) / 4.15
Utilization = bigness_factor * boil_time_factor
IBU = (hop_oz * alpha_acid% / 100 * utilization * 7489) / batch_gallons
The constant 7489 converts the result to mg/L (IBU). This formula gives utilization as a decimal; multiply by 100 for percentage display.
IBU style reference
- Light lager: 5-15 IBU
- Wheat beer: 10-20 IBU
- Pale ale: 25-45 IBU
- IPA: 40-70 IBU
- Double / Imperial IPA: 60-100+ IBU
- Stout / porter: 20-50 IBU
Beer IBU: frequently asked questions
What is IBU in beer?
IBU stands for International Bitterness Units and measures the concentration of iso-alpha acids in beer - the compounds responsible for bitterness. A light lager may be 8-12 IBU, a pale ale 25-45 IBU, and an imperial IPA 65-100+ IBU. Human perception of bitterness varies significantly by individual.
What is the Tinseth formula?
The Tinseth formula, developed by Glenn Tinseth, calculates IBU as: IBU = (oz hops * alpha acid% * utilization%) / (wort volume in gallons * 0.7489). Utilization depends on boil time and wort gravity. It is one of the most widely used homebrewing IBU formulas.
What affects hop utilization?
Utilization increases with longer boil times (peaking around 90-120 minutes). Higher wort gravity reduces utilization because more sugars compete with alpha acid isomerization. Late additions (0-10 min) have very low utilization (5-10%) and contribute mostly aroma.
How does batch size affect IBU?
IBU is inversely proportional to wort volume. The same hop addition in a 5-gallon batch has twice the IBU as in a 10-gallon batch. Scale your hop additions proportionally when scaling recipe size.
What is the BU:GU ratio?
The BU:GU (Bitterness-to-Gravity) ratio compares IBU to original gravity points. A ratio of 1.0 (e.g., 50 IBU / 1.050 OG = 50 gravity points) indicates a balanced beer. Ratios above 1.0 are more bitter; below 0.5 are sweeter.
Official sources
- Tinseth, G.: Hop Utilization in the Real World.
- American Society of Brewing Chemists: ASBC Methods of Analysis.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.