Hydrometer Temperature Correction

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 in a Trial Jar
A Hydrometer in a Trial Jar

Hydrometer readings are based upon the density of water (and what is dissolved in water) at a specific temperature. This density changes with change in 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.

Hydrometer Calibration

Glass Hydrometers are typically calibrated to either 15°C (59°F) or 20°C (68°F). The calibration temperature should be clearly labelled on the hydrometer. This is not something that can be adjusted.

Electronic Hydrometers

Electronic Hydrometers such as a Tilt or an iSpindel provide a great way to get gravity and temperature readings via WiFi/Bluetooth without opening a Fermentation Vessel (FV). This is quite useful in avoidance of potentially contaminating the FVs contents. Additionally, the information from the hydrometer can stream directly to devices like and Smart Phone, Tablet, Laptop Computer, etc. These types of hydrometers are excellent at showing trends, but can sometimes lack in accuracy.

Like most electronic devices, they do need to be calibrated when new, after changing the batteries, and then every so often. Instructions on how to calibrate vary by manufacturer.

Hydrometer Temperature Correction
Hydrometer Temperature Correction