Hydrometer Temperature Correction Calculator
Enter your hydrometer reading and the sample temperature to get the corrected specific gravity at the calibration temperature. Brix and Plato equivalents included. Nothing uploaded.
Reading
Corrected Reading
Learn more: hydrometer temperature correction and gravity scales
How temperature affects hydrometer readings - the physics of density change
Hydrometers measure specific gravity by floating at a depth proportional to liquid density. All hydrometers are calibrated at a reference temperature, typically 20°C (68°F). When you measure a sample at a different temperature, the sample's density is different, causing the hydrometer to float at a different level - giving an incorrect reading. At 30°C, a true SG of 1.050 might read as 1.052 (about 2 points high). At 40°C, the error can exceed 5 points. These errors accumulate into significant ABV miscalculations, so temperature correction is essential for accurate brewing.
Specific gravity, Brix, and Plato - three ways to measure the same thing
Specific gravity (SG) measures the density of a liquid compared to pure water at 4°C. Brix measures the percentage of dissolved sugars by weight and is commonly used in winemaking and juice production. Plato (degrees Plato) is similar to Brix and is used in brewing. For the same liquid at the same temperature, these three measurements are mathematically equivalent - the calculator converts between them so you can use whichever scale your equipment or software expects. Homebrewers often use SG and ABV; winemakers often use Brix; commercial breweries use Plato.
Hydrometer calibration temperatures and when they matter
Most modern hydrometers are calibrated at 20°C, but older American hydrometers were calibrated at 15°C (59°F). The calculator lets you select which standard your hydrometer follows. If your hydrometer is unmarked, assume 20°C. The smaller the temperature difference between your sample and the calibration temperature, the smaller your correction factor - so chilling your sample to 20°C before measuring eliminates the need for correction altogether.
FAQ
Why do I need to correct for temperature?
Temperature changes liquid density. A warm sample reads lower (floats higher) than the same liquid at calibration temperature. Even a 2-3 point SG error translates to a 0.5% ABV error in final calculations - large enough to be noticeable in the finished beer or wine.
Should I chill my sample or use a calculator?
Chilling to calibration temperature is ideal because it eliminates error. But if your sample is hard to cool (e.g., a carboy of fermenting beer), the correction calculator is the practical solution - measure the temperature and correct the reading.
Can I measure gravity with a refractometer instead?
Refractometers have built-in temperature compensation and work well for pre-fermentation OG readings. However, alcohol in fermented samples creates significant errors on refractometers - hydrometers remain the gold standard for FG measurements after fermentation.