Hydrometer Temperature Correction Calculator
Correct Specific Gravity (SG) readings for temperature variance in homebrewing and distilling. Supports SG and Brix with auto-calibration logic.
About
Hydrometers are precision glass instruments calibrated to read density accurately at a specific temperature, typically 20°C (68°F) or 15.6°C (60°F). When a wort or wash is measured at a higher or lower temperature, the liquid's density changes due to thermal expansion or contraction, resulting in a false reading.
This calculator applies a polynomial correction algorithm to adjust the SGmeasured to the SGtrue. It is essential for brewers to obtain accurate Original Gravity (OG) and Final Gravity (FG) numbers, which directly impact the calculation of Alcohol by Volume (ABV) and attenuation efficiency.
Formulas
The correction formula utilizes a polynomial derived from the thermal expansion of water. For a hydrometer calibrated at temperature Tcal, the corrected gravity CG is derived from the measured gravity MG and measured temperature Tm (in Fahrenheit):
Accurate corrections generally hold for SG between 0.990 and 1.130.
Reference Data
| Temp °C | Temp °F | SG Correction (Add/Sub) | Example Reading 1.050 becomes |
|---|---|---|---|
| 10 | 50 | -0.002 | 1.048 |
| 15 | 59 | -0.001 | 1.049 |
| 20 | 68 | 0.000 (Calibrated) | 1.050 |
| 25 | 77 | +0.001 | 1.051 |
| 30 | 86 | +0.003 | 1.053 |
| 35 | 95 | +0.005 | 1.055 |
| 40 | 104 | +0.007 | 1.057 |
| 50 | 122 | +0.011 | 1.061 |