Spirit Dilution Calculator

No -- Water to Add is floored at zero rather than showing a negative number, because adding water can only dilute a spirit -- it can never raise its ABV. If your target is at or above your current strength, the calculator is telling you there's nothing to add; you'd need to blend in higher-proof spirit or re-distill to raise ABV, which is a different process entirely from the water-dilution math this tool performs.

When ethanol and water mix, the resulting volume is slightly less than the sum of the two separate volumes, because the molecules pack together more efficiently than when kept apart -- an effect chemists call volume contraction. The real effect's size varies with the mixture's ABV, but this calculator applies a flat 3% reduction uniformly (whenever water is actually being added) as a simplified approximation rather than modeling that variation, so Adjusted Final Volume is a closer estimate than the simple arithmetic sum, though not an exact one.

Target ABV sits in the denominator of the dilution formula (Current ABV divided by Target ABV, minus 1), so its effect on Water to Add isn't linear -- lowering an already-low target ABV requires proportionally much more water than the same size drop starting from a higher target. Going from 40% to 30% target ABV, for example, requires noticeably more added water than going from 60% to 50%, even though both are 10 percentage-point drops.

Spirit Volume scales Water to Add proportionally -- doubling Spirit Volume exactly doubles the water needed to reach the same Target ABV, since the underlying ratio (Current ABV divided by Target ABV, minus 1) stays the same regardless of how much spirit you start with. It's Current ABV and Target ABV together that determine the dilution ratio itself; Spirit Volume just scales that ratio to your actual batch size.