About Hydrometer Temperature Correction
This is a calculator for Hydrometer Temperature Correction. Hydrometers are used in homebrewing primarily from taking the gravity (i.e. density) of wort before pitching yeast and taking the gravity again after the yeast have finished. These two measurements are called the Original Gravity (OG) and the Final Gravity (FG) respectively. Once these numbers are recorded, they are then input to a calculator to determine percent of alcohol content by volume (%ABV).
Hydrometer readings are based upon the change in density of water (and what is dissolved in water) at a specific temperature. If you take your Original Gravity (OG) and Final Gravity (FG) at similar temperatures somewhere around the calibration point, there’s no need for a temperature correction. However, if the Original Gravity (OG) and/or Final Gravity (FG) temperatures taken are significantly different temperatures and far enough away from the calibration temperature, your calculated %ABV will be incorrect.
Hydrometers are typically calibrated to either 15°C (59°F) or 20°C (68°F). The calibration temperature should be clearly labeled on the hydrometer. This is not something that can be adjusted.