This calculator can be used to correct hydrometer readings when readings are taken at a temperature that is different than the hydrometer calibration temperature.
The specific gravity of wort changes with temperature, and the readings marked on all hydrometers are valid only if the wort temperature is at the calibration temperature of the hydrometer when the reading is taken. Homebrewers often take gravity readings at other temperatures for convenience. Fortunately, these readings can be corrected provided the temperature of the wort is measured when the gravity is measured, and the calibration temperature of the hydrometer is known. This calculator will adjust gravity readings taken at a temperature different than the calibration temperature of the hydrometer.
The formula used for this calculation is as follows:
CG = MG * ((1.00130346 – 0.000134722124 * T + 0.00000204052596 * T^2 – 0.00000000232820948 * T^3) / (1.00130346 – 0.000134722124 * TC + 0.00000204052596 * TC^2 – 0.00000000232820948 * TC^3))
In this formula CG represents the corrected gravity reading in specific gravity units and MG reprsents the measured gravity reading, also in specific gravity units. T represents the wort temperature at the time the reading was taken in °F, and TC represents the calibration temperature of the hydromter, also in °F.