Proofing Down Water Addition Calculator

Work out proofing down water addition instantly with clear inputs, formula shown and shareable results.

About Proofing Down Water Addition Calculator

Alcohol is conserved when diluting, so the final volume is pure alcohol divided by the target strength fraction, and water to add is the difference from the starting volume. In practice ethanol and water contract slightly on mixing, so the true final volume is a little less and strength must be verified after blending.

Formula

Proofing down

Final volume = spirit volume x current ABV / target ABV; water = final volume - spirit volume

Worked example

With the default values below, Proofing Down Water Addition Calculator returns Water To Add of 57.500. Change any input above and every figure here is recalculated in your browser.

Inputs used

Spirit Volumeminimum 0 L: 100 L
Current Strengthaccepts 0–100 %: 63 %
Target Strengthaccepts 0–100 %: 40 %
Bottle Sizeminimum 0 mL: 700 mL

Results

Water To Add: 57.500
Final Volume: 157.500
Pure Alcohol Content: 63.000
Bottles Produced: 225.0

Step by step

1Values used
2Proofing down
3Water To Add= 57.500
4Final Volume= 157.500
5Pure Alcohol Content= 63.000
6Bottles Produced= 225.0

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Declared alcohol strength is legally regulated with narrow tolerances and determines excise duty. Verify by an approved method at the reference temperature.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Declared alcohol strength is legally regulated with narrow tolerances and determines excise duty. Verify by an approved method at the reference temperature.

Frequently Asked Questions

Why verify strength after dilution?

Volume contraction on mixing means the arithmetic slightly under-predicts strength. Custody and labelling require measurement with a calibrated hydrometer or density meter at a controlled temperature.

Does water quality matter?

Yes. Demineralised or very soft water avoids haze from calcium and magnesium reacting with fatty acids, and avoids chlorine and off-flavours. Hard tap water can cloud a spirit permanently.