Hydrometer Temperature Correction Calculator

How it is calculated

The tool uses the density of water at the two temperatures, taken from a third-degree polynomial in degrees Fahrenheit, as the correction factor:

f(T) = 1.00130346 − 0.000134722124·T + 0.00000204052596·T² − 0.00000000232820948·T³

corrected gravity = measured gravity × f(sample temp) / f(calibration temp)

Both temperatures are in °F. The sample temperature is the real temperature of the liquid in the cylinder, and the calibration temperature is printed on your hydrometer (often 60 °F or 68 °F). The result is shown with three decimals. If the two temperatures are equal, the reading comes back unchanged. The tool does not check the temperatures against the freezing and boiling point of water, so an unrealistic entry still returns a number. The correction is for the density change of water-like wort and must; it is not an alcohol or sugar correction.

Common mistakes

• Entering Celsius temperatures. A 25 °C sample typed as 25 and a 15.6 °C calibration typed as 15.6 are read as 25 °F and 15.6 °F, giving a silently wrong answer (1.049 instead of 1.052). Convert to °F first.
• Typing the gravity as 1050 or 50 instead of 1.050. The field expects the specific gravity, so 1050 returns 1,052.446.
• Entering the temperature of the room or of the fermenter instead of the liquid in the test jar, which is the one that matters.
• Entering the wrong calibration temperature. Hydrometers differ (60 °F or 68 °F), so check the scale or the box.
• Applying the correction twice, or to a reading that was already taken at the calibration temperature, when the tool's answer would just return the same figure.