Hydrometer Temperature Correction Calculator

About this calculator

Hydrometers are calibrated to give accurate specific-gravity readings only at one reference temperature — commonly 60°F (15.6°C) or 68°F (20°C) depending on the instrument — because liquid expands as it warms, becoming less dense, which makes a hot sample read artificially low and a cold sample read artificially high compared to its true gravity at the calibration temperature. The correction applies a temperature-adjustment formula (or lookup table) based on the difference between the sample's actual temperature and the hydrometer's calibration temperature to recover the true specific gravity.

Homebrewers and winemakers take this correction seriously because specific gravity readings taken before and after fermentation are used to calculate alcohol content and track fermentation progress, and an uncorrected reading taken from a warm wort or must sample can throw off both the tracked attenuation and the final ABV calculation. It's a standard step any time gravity is checked with a wort or must sample straight out of the kettle or fermenter rather than cooled to the hydrometer's reference temperature.

This calculator takes your hydrometer reading, the sample's actual temperature and the hydrometer's calibration temperature, and returns the corrected specific gravity.