ABV ↔ Proof Converter and Alcohol Dilution Calculator

Convert between ABV and US proof, and calculate how much water you need to add to reach a target bottling strength.

ABV and proof conversion

ABV → Proof

80.0

Proof → ABV

40.0%

Water to add

187.5 mL water

Formulas

Proof = ABV × 2 (US system)
ABV = Proof ÷ 2
Dilution uses C1V1 = C2V2 where concentration is alcohol by volume.