Hop Bitterness IBU Calculator
Estimate Tinseth bitterness from several whole-hop boil additions, their alpha-acid percentages and times.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Evaluate the Tinseth empirical utilization for each addition and add its estimated iso-alpha contribution per final liter.
Utilization=1.65×0.000125^(SG−1)×(1−exp(−0.04t))/4.15; IBU=Σ(g hops×alpha fraction×utilization×1000)/liters
Worked example
With zero boil time an addition contributes zero in this model. Doubling a hop mass doubles only that addition’s estimated contribution.
Assumptions and input details
Use equal-length lists, 0–30% alpha acids and 0–240 minute boil times. Whole-hop boil model with no pellet multiplier, whirlpool, dry-hop, cooling-time or measured sensory-bitterness correction. IBU is an estimate, not measured bitterness.
References: brewdio: documented Tinseth implementation
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
The 36 volume definitions distinguish US liquid, US dry and Imperial measures. Cups carry an explicit definition. Japanese shō is 2401/1331 L and a gō is one tenth of it; the explicitly labelled 180 mL rice cup is separate.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · UK Imperial definitions · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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