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Dilution calculator: how much water to hit a proof

Water is the one ingredient with a proof of zero, which makes its math exact. Enter what you have and where you want to land.

The formula

Alcohol is conserved; water spreads it through more volume. 20 oz at 110 proof needs 2 oz of water to reach 100. Full explanation and the round-trip check.

Small amounts, big leverage

At bottle scale, water is powerful: a shot glass of water in a full bottle is a decision, not a rounding error. Add in small increments, taste, and record each one.

The caveat, honestly

Ethanol and water contract slightly on mixing, so volume math runs a small fraction off from a distillery lab's mass-based figure. For home purposes the error is far below your measuring cup's precision.