Correct hydrometer readings for temperature differences. Hydrometers are calibrated at a specific temperature — if your sample is warmer or cooler, the reading needs adjustment.
A hydrometer measures the density (specific gravity) of a liquid by how deeply it sinks. However, liquid density changes with temperature — warmer liquids are less dense, causing the hydrometer to sink deeper and read lower than the actual gravity.
This calculator uses a polynomial correction formula based on the thermal expansion of water and wort:
correction(T) = 1.313454 − 0.132674×T + 2.057793×10³×T² − 2.627634×10&sup5;×T³
The difference between the correction at measurement temperature and calibration temperature is applied to your reading to yield the true specific gravity.