Gravity temperature correction calculator

A hydrometer floats at a depth set by the density of the liquid, and it only reads true at the one temperature it was calibrated to — the number etched on its stem, usually 60 °F on a US hydrometer or 68 °F (20 °C) elsewhere. Pull a sample straight off the chiller and read it warm and the reading comes out low; read it cold and it comes out high. The Gravity Temperature Correction calculator turns the reading you actually took into the reading you would have got at the calibration temperature.

It's free, needs no account, and computes in your browser.

This is not the Temperature Correction calculator. The one called Temperature Correction on the hub corrects a proof reading on spirits, and it follows the official 27 CFR §30.61 method. This page corrects a specific gravity reading — a wort, must or juice sample — using a homebrewing convention. They are different calculations. Each page links to the other.

Open the calculator

• On the public site: in the top navigation choose Tools, then on the Gravity Temperature Correction card choose Open calculator.
• Inside the app: in the navigation choose Tools, then on the Gravity Temperature Correction card choose Open calculator.

Correct a reading

1. In Hydrometer reading (SG), enter the gravity your hydrometer showed — for example 1.048.
2. In Sample temperature, enter how warm the sample was, and pick °F or °C beside it. (Inside the app the unit starts on whichever system your workspace uses.)
3. In Hydrometer calibrated at, choose the temperature etched on your hydrometer's stem — 60 °F (15.6 °C) or 68 °F (20 °C). Most US hydrometers say 60 °F, which is the default.
4. Corrected gravity appears as soon as the reading and the temperature are both valid, with a line underneath saying how much your reading moved.

If a value is out of range the field says so (Enter a specific gravity between 0.98 and 1.2. or Enter a temperature between 32 and 212 °F.) rather than showing a made-up answer.

Worked example

A wort sample reads 1.048 at 80 °F, on a hydrometer calibrated to 60 °F:

1. Hydrometer reading (SG): 1.048
2. Sample temperature: 80, unit °F
3. Hydrometer calibrated at: 60 °F (15.6 °C)

The calculator shows Corrected gravity 1.050, and the line under it reads "Your reading of 1.048 corrects by +0.002." That's two gravity points — roughly a quarter of a percent of finished alcohol on a normal beer, and enough to move which side of a style guideline you land on.

When the answer gets shaky

If the sample is more than 30 °F from the hydrometer's calibration temperature, the calculator adds a note. The correction still applies, but it's an approximation built on the density of water rather than of your particular sugar solution, and it gets rougher the further out you go. The honest fix is to cool the sample closer to the calibration temperature and read it again.

What it assumes

• A glass hydrometer. A refractometer measures refractive index rather than density; it needs an entirely different correction, and (once fermentation has started) a wort-correction factor as well. Don't feed a refractometer reading into this page.
• Water's density curve. The formula is the standard hydrometer temperature-adjustment convention — a cubic fit to the density of water, the same one behind the printed correction tables in homebrewing texts and the widely used Brewer's Friend calculator. It's a reference estimate, not an official measurement, and there's no government formula for it.

When to reach for it

Any time you read a gravity somewhere other than your hydrometer's calibration temperature — an original gravity taken before the wort is fully chilled, a final gravity on a warm summer day, a juice reading in a cold garage. Correct it first, then use the corrected number everywhere else: feed it into the ABV-from-gravity calculator, the Cider ABV calculator, or your batch's stage log. Recording the raw warm reading is what puts a wrong number in the notebook permanently.