Free tool
Took a gravity reading when your sample was warmer or cooler than your hydrometer's calibration temperature? Enter the reading and the temperatures to get the true specific gravity.
Most hydrometers are calibrated at 20°C. Check the slip inside yours if unsure.
A hydrometer measures density, and density changes with temperature. Liquid expands when warm and contracts when cold. Your hydrometer is calibrated to be spot on at one temperature (usually 20°C), so a reading taken at any other temperature needs a small correction.
This calculator applies the standard correction formula based on how water's density changes with temperature, giving you the gravity your hydrometer would have shown at its calibration point.
Hydrometers are calibrated to read accurately at one temperature (usually 20°C). Liquid expands as it warms and contracts as it cools, changing its density, so a reading taken at a different temperature is slightly off until you correct it.
Most homebrew hydrometers are calibrated at 20°C (68°F), though some older or US models use 15.5°C (60°F). The figure is usually printed on the paper slip inside the hydrometer.
Near the calibration temperature, very little. But a reading taken on a hot sample straight off the boil, say 30-40°C, can read low by 0.002-0.005, which is enough to throw off your ABV estimate.
Cooling your sample to the calibration temperature is the most accurate approach. This calculator is for when that is not practical. It gives you the corrected figure from a reading taken warm.
Demijohn Journal tracks your gravity and temperature readings over a batch and works out ABV as you go. Free, in your browser.
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