Hop Utilization (Tinseth)

How it is calculated

The tool uses the Tinseth model, which multiplies two factors: utilization = 1.65 × 0.000125(SG − 1) × (1 − e−0.04 × t) ÷ 4.15. SG is the boil gravity as a decimal (1.050) and t is the time the hops stay in the boil, in minutes. The first part, the bigness factor, shrinks as gravity rises; the second, the time factor, rises towards a ceiling the longer the boil. Dividing by 4.15 scales the product so the answer is the fraction of alpha acids isomerized, shown as a percentage with two decimals. A time of zero gives 0.00 %. Gravity must be between 0.980 and 1.200 and the time cannot be negative; otherwise there is no result. The output is the utilization only: it is not IBU, which also needs alpha-acid percentage, hop weight and batch volume.

Common mistakes

• Entering the gravity as points, for example 1050 or 50. The field takes the decimal SG, 1.050, and values like 1050 or 50 are outside the accepted 0.980 to 1.200 range and show no result.
• Entering the original gravity of the full batch when the hops boil in a partial-volume or concentrated wort. Use the gravity of the wort actually boiled with the hops.
• Treating the percentage as IBU. This tool gives only the utilization; IBU also depends on alpha acid, grams and litres.
• Entering the total boil length for a late addition. The time is how long the hops spend in the boil, so a 5 minute flavour addition is 5, not 60, and using 60 gives a far higher figure.
• Applying it to dry-hop or whirlpool additions. The formula describes isomerization during a boil only.