Alcohol Dilution Calculator
Whether you are cutting down a barrel-strength bourbon, proofing a fresh distillate, or diluting high-proof spirits for cocktail use, this calculator tells you exactly how much water to add to reach your target ABV.
Here's how dilution works:
Final Volume = (Current ABV / Target ABV) x Current Volume Water to Add = Final Volume - Current Volume
This is based on the standard dilution equation (C1 x V1 = C2 x V2), where the amount of pure alcohol stays constant and only the total volume changes.
Example: You have 750 mL of 60% ABV (120 proof) spirit and want to dilute it to 40% ABV (80 proof):
- Final volume = (60 / 40) x 750 = 1,125 mL
- Water to add = 1,125 - 750 = 375 mL
Important notes for distillers:
- Use distilled or filtered water. Tap water with chlorine or high mineral content can cause cloudiness (louching) and off flavors.
- Add water slowly. Pour the water into the spirit, not the other way around, and add it gradually over several minutes. Rapid dilution can cause haze.
- Temperature matters. The standard reference temperature for measuring proof is 60F (15.6C). Alcohol/water mixtures are slightly non-ideal, meaning the final volume may be 2-3% less than the simple calculation predicts due to molecular contraction. For precise proofing, measure ABV with a hydrometer after dilution at the reference temperature.
- Let it rest. After dilution, let the mixture sit for at least 24-48 hours before final proof measurement. The alcohol and water need time to fully integrate.
For home cocktail use, this level of precision is not necessary. The calculator gives you a close-enough answer for practical purposes.