Find out how much water to add to spirit or distillate to get 40% vodka, a 70% infusion base or any other strength. The calculator uses OIML density tables, so it includes contraction – more accurate than a simple proportion.
What is alcohol contraction?
When alcohol and water are mixed, the molecules pack more tightly and the mixture's volume is smaller than the sum of the volumes – by up to 3–4%. The simple formula V × (A/B − 1) ignores this, so it gives too little water and too high a strength.
How do I dilute alcohol properly?
Use demineralised, distilled or low-mineral water – hard water causes cloudiness. Pour the alcohol into the water, not the other way round, mix thoroughly and let it rest for at least a day. Check the strength with an alcoholmeter at 20°C.
Two calculation modes
“I have” mode tells you how much water to add to the alcohol you have. “I want” mode tells you how much alcohol and water to measure out to get a set amount of finished product, e.g. 0.5 l of 40% vodka.
How we calculate
We calculate from the mass of pure ethanol using density tables for water–ethanol mixtures at 20°C, so the result includes contraction (the mixed volume is smaller than the sum of the components). For comparison we also show the result of the simplified formula V × (A/B − 1).
Frequently asked questions
How much water should I add to 1 litre of 96% spirit to get 40%?
About 1.47 litres of water. You will get about 2.4 litres of alcohol – less than the sum of the components because of contraction.
Why does alcohol turn cloudy after dilution?
Usually because of hard water or fusel oils in the distillate. Use demineralised or low-mineral water and pour the alcohol into the water, not the other way round.
Why does alcohol warm up when mixed with water?
Mixing alcohol with water releases heat and the volume shrinks. After dilution wait until the mixture cools to about 20°C and only then measure the strength.
Should diluted alcohol be left to rest?
Yes. After dilution leave the alcohol for a few days in a closed vessel – the taste evens out and any sediment settles.
How much water for 0.5 l of spirit to make vodka?
Add about 0.74 l of water to 0.5 l of 96% spirit – you will get about 1.2 l of 40% alcohol.
What water should I use for dilution?
Preferably demineralised or low-mineral still water. Tap water can leave sediment and a chlorine smell.