Hydrometer Temperature Correction
Hydrometers are calibrated to one temperature - usually 59 °F (15 °C). Enter your reading and the sample temperature to get the corrected specific gravity instantly.
Corrected reading
Value must be between 23 and 203.
How the correction works
Warm liquid is less dense, so a warm sample lets the hydrometer sink deeper and read low; a cold sample reads high. The calculator applies the standard polynomial correction used across homebrewing, calibrated to 59 °F (15 °C), and is most accurate between 50 °F and 110 °F (10-43 °C).
Corrected readings are the raw material for every other number in brewing: use them in the ABV calculator, or convert a refractometer sample with the Brix to SG calculator.
Frequently asked questions
What temperature is my hydrometer calibrated for?
Most modern homebrewing hydrometers are calibrated to 59 F (15 C); some use 68 F (20 C) or 77 F (25 C). The calibration temperature is printed on the paper scale inside the instrument. This calculator uses the standard 59 F polynomial - if yours is calibrated differently, the correction is close but not exact far from room temperature.
Why does a warm sample read low?
Warm liquid is less dense, so it buoys the hydrometer less and the instrument sinks deeper, pointing to a lower gravity than the true value. A cold sample does the opposite and reads high. The further you are from the calibration temperature, the bigger the error - roughly 3 SG points at 20 F off calibration.
How accurate is the correction at extreme temperatures?
The polynomial is dependable between about 50 F and 110 F (10-43 C). Beyond that range the model drifts: near freezing or above 140 F (60 C) the correction is an estimate, not a measurement. When accuracy matters, cool a small sample to the calibration temperature and read it there.
Does the correction work for finished beer with alcohol?
Yes, well enough for brewing decisions. Alcohol lowers density while dissolved sugars raise it, and the empirical polynomial was built from real wort and beer samples across that range. It is the same correction homebrewing software applies when you log a warm reading.