Alcohol & ABV
How to Calculate Alcohol Dilution
Use a simple strength-and-volume relationship to estimate dilution, then verify the blend with measurement.
Use compatible strength units
For an initial estimate, multiply the starting volume by its alcohol fraction and divide by the target alcohol fraction to estimate final volume. Subtract the starting volume to estimate the water addition.
A percentage can be used in place of a fraction if both strengths use the same scale. The calculation assumes the starting liquid and target are measured consistently.
Account for volume contraction
Ethanol and water do not always add to their original combined volumes. The simple formula therefore estimates rather than guarantees the final volume or strength.
Blend gradually, allow temperature to stabilize, and measure with a suitable instrument. Follow local laws and never use this calculation to assess unknown or non-food-grade alcohol.
Know when this is not appropriate
This is a dilution equation only. It does not purify a liquid, remove contaminants, make an unsafe source suitable for consumption, or replace legal and safety requirements.
For products where exact strength matters, use a validated method and calibrated measurement equipment.