An alcoholmeter is calibrated for 20°C. If you measure warm distillate straight from the condenser or cold spirit from the cellar, enter the reading and temperature – the calculator gives the true strength.
Why does temperature change the reading?
An alcoholmeter measures liquid density. Warm alcohol expands and becomes lighter, so the instrument sinks deeper and shows too high a strength. Cold alcohol reads too low. For 40% alcohol the difference is about 0.3–0.4 percentage points per degree.
How do I measure accurately?
Use a measuring cylinder, read at the bottom of the meniscus and measure the temperature of the same sample. For best accuracy bring the sample to 15–25°C before applying the correction.
How we calculate
An alcoholmeter measures density. We determine the density corresponding to the reading at 20°C and then find the strength whose density at the measuring temperature is identical (including thermal expansion of the mixture). Accuracy approx. ±0.3% vol – use official tables for legal purposes.
Frequently asked questions
How much does the reading change per degree?
For 40% alcohol about 0.3–0.4% vol per °C. Warm alcohol reads higher, cold alcohol lower.
How do I check whether my alcoholmeter is accurate?
Put it in distilled water at 20°C – it should read 0%. You can also compare the reading with a second alcoholmeter in the same sample.
How do I look after an alcoholmeter?
After each measurement rinse it with water and wipe it with a soft cloth. Do not wash it in hot water and keep it in its case – even a small crack or dirt will distort the reading.
Can I measure a liqueur with an alcoholmeter?
No – sugar and extract increase the density, so the reading will be too low. An alcoholmeter works correctly only in a pure mixture of alcohol and water.