A hydrometer is only accurate at its calibration temperature. Read a hot or cold sample and the number is off, sometimes by enough to matter. Enter your reading and its temperature below to correct it.
Correct your hydrometer reading
Why the correction matters
Liquid changes density with temperature, so a warm sample sits lighter and reads low, while a cold one reads high. Straight off the kettle a reading can be off by several gravity points, which then throws off your OG, your efficiency, and your final ABV.
The fix is either to cool the sample to the calibration temperature before reading, or to read it as-is and correct it here. Both get you to the same true gravity.
Finding your calibration temperature
It is printed on the hydrometer or its paperwork, usually 68F (20C), sometimes 60F (15.6C). Enter the value your hydrometer states so the correction is accurate.
The further your sample is from that temperature, the bigger the correction. Near the calibration point it is tiny; a sample at 100F against a 68F hydrometer shifts by roughly 0.005.
Frequently asked questions
Why correct a hydrometer reading?
A hydrometer is only accurate at its calibration temperature. A hot sample reads low and a cold one reads high, so a reading straight off the kettle can be off by several points. This corrects it back to a true gravity.
What is the calibration temperature?
It is printed on the hydrometer, usually 68F (20C) or sometimes 60F (15.6C). Enter the one your hydrometer states so the correction is accurate.
How big is the error?
Small near the calibration temperature, larger as the gap grows. A sample at 100F read against a 68F hydrometer is off by roughly 0.005, enough to matter for an accurate OG or ABV.
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