Alcoholmeter temperature correction calculator

Spirit swells as it warms, so a warm jar reads high on an alcoholmeter and a cold one reads low. Enter the reading and the spirit’s temperature for its true strength.

How it works

It uses the OIML R 22 International Alcoholometric Tables, which the EU adopted in law. From the reading and the temperature it works out the spirit’s density, allows for the glass instrument swelling with the heat, and finds the mix of alcohol and water with that density.

The answer is the strength at the instrument’s own calibration: % ABV at 20 °C for a 20 °C alcoholmeter, or proof at 60 °F for a US proof hydrometer.

Worked examples

• 65.0% read at 26.0 °C on a 20 °C alcoholmeter is 62.9% at 20 °C: the warm spirit read 2.1% high.
• 40.0% read at 25 °C is 38.0%, so bottling it as 40% would leave it two points weak.
• 80 proof read at 68 °F on a 60 °F proof hydrometer is 76.4 proof at 60 °F.

Good to know

• The tables cover −20 to 40 °C (−4 to 104 °F) and 0 to 100% (0 to 200 proof). Read at room temperature if you can.
• Sugar or oak extract in spirit makes it read low whatever the temperature, so this suits clear spirit of alcohol and water, not sweetened or aged spirit.
• On a 60 °F proof hydrometer this is the OIML answer at 60 °F. US gauging uses the TTB’s own tables, which agree to within about 0.2 proof between 41 and 100 °F.
• Let the alcoholmeter float free of the cylinder’s side, and read at the flat surface of the spirit rather than the curve climbing the stem.