Dilute a spirit or high-proof alcohol to a target strength: enter the starting volume and both strengths, in ABV or US proof, and read off how much water to add.
Enter the starting volume and strength and the strength you want; the result updates as you type.
Strength in
Adding water changes the volume but not the amount of ethanol, so the dilution equation applies: final volume = starting volume × (current strength ÷ target strength), and the water to add is the difference. Going from 1 L at 95% to 70% means a final volume of about 1357 mL, so roughly 357 mL of water.
Ethanol and water molecules pack tighter together than apart, so mixing them loses up to about 3% of the combined volume — 1 L of ethanol plus 1 L of water yields roughly 1.92 L. The calculator, like every C₁V₁-based tool, ignores this, which is why the final volume is labeled approximate. For bottling-strength precision, distillers work by mass with density tables.
ABV states the ethanol share of the volume directly; US proof is simply twice the ABV, so 80 proof is 40% ABV and 151 proof is 75.5% ABV. The calculator accepts either and converts behind the scenes. Note that the historic British proof scale is different (100 British proof ≈ 57.1% ABV) and is not used here.
To turn 95% ethanol into the 70% mix commonly used as a sanitizer: per liter of 95%, add about 357 mL of water for roughly 1.36 L of 70%. Let it rest, measure, and top up with water to the exact final volume if the shrinkage matters for your use.
The water to add is V₁ × (C₁ ÷ C₂ − 1), with strengths entered in ABV (proof is halved first). This is the standard C₁V₁ = C₂V₂ approximation, which treats volumes as additive.
Because ethanol–water mixing is non-additive, the true final volume is slightly smaller than calculated — up to about 3% at mid strengths. The calculator states this next to the result; precise work, such as bottling at a legal strength, should be done by mass against OIML alcoholometry tables.
This calculator is for general reference. Commercial bottling strengths are regulated — verify them by mass measurement against official alcoholometry tables.
Short answers to the questions people ask most about diluting alcohol.