Input
How to use this calculator
Enter the gravity shown by the hydrometer, the temperature of the sample and the instrument calibration temperature. Most hydrometers are calibrated at a stated reference temperature; use the value printed on the instrument or its documentation.
Take a representative sample, remove foam and read the meniscus consistently. Correct the reading before using it for OG, FG, ABV or attenuation calculations. The calculator accepts Celsius values on this public page.
How the calculation works
The current implementation converts the measured and calibration temperatures to Fahrenheit, evaluates a polynomial density factor for each temperature and applies their ratio to the measured SG. The output includes corrected SG and the correction amount.
This corrects temperature response; it does not correct a dirty, damaged or poorly calibrated hydrometer. Wort and beer composition can also introduce small instrument-specific errors, especially outside the instrument range.
Example calculation
A reading of 1.045 from a 22 C sample with an instrument calibrated at 20 C receives a small temperature correction. The corrected SG is the value to carry into an ABV or attenuation calculation.
Understanding the result
Hydrometer correction keeps measurements comparable when sample temperature changes. It is especially important when comparing a hot-side OG reading with a cooler fermentation sample.
The correction is normally modest, but a modest error in both OG and FG can move the estimated ABV. Keep the raw reading and corrected value in your brew notes so the measurement history remains auditable.
Common mistakes
- Confusing sample temperature with calibration temperature.
- Reading foam or bubbles as the meniscus.
- Using a correction table for a different instrument.
- Skipping correction when comparing OG and FG.
Frequently asked questions
What is calibration temperature?
It is the temperature at which the hydrometer was designed to read the stated gravity accurately.
Should I correct a refractometer with this tool?
No. Refractometers need Brix and alcohol correction; use the dedicated Refractometer tool.
Does correction fix an inaccurate hydrometer?
No. It only adjusts the temperature response of an otherwise suitable instrument.
Related brewing guides
Related tools
This public tool
A quick, free, no-login estimate for a single calculation — nothing is saved.
Inside Beer Control
The same calculation stays linked to your recipe, ingredients, equipment and brew session, so targets and measured values travel together through the whole workflow.
Build recipes with Beer Control