Fermentation alcohol estimate
Estimate beer ABV and apparent attenuation from original and final hydrometer gravity. Drag the graph handles to change inputs and explore the result.
Your inputs
The editable example is illustrative. Enter your own dimensions, operating data, prices, and fees. Results update as you edit.
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How it works
- ABV ≈ 131.25 × ( − ); Apparent attenuation = 100 × ( − ) / ( − 1)
Input and formula key
Your result
Complete the inputs to see your result.
Assumptions and limitations
Enter specific gravity readings corrected to the hydrometer’s calibration temperature. Raw refractometer readings after fermentation need a separate alcohol correction. The 131.25 factor is an approximate brewing convention, not a laboratory or labeling determination. Apparent attenuation can exceed 100% below SG 1. Example: 1.050 to 1.010 estimates 5.25% ABV and 80% attenuation.
Sources
- The Open University — measuring alcohol using gravity Sources reviewed: 2026-10-22
- Grainfather — original and final gravity Sources reviewed: 2026-10-22
