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Basics and units

Gravity correction for temperature

A reading at 30 °C underestimates the gravity by 2 to 3 points. Correct it before you write it down.

From 0 to 100.

Result

Fill in the values and run the calculation, or try the example.

This is the calculation Krausi uses. Create an account to save it in a recipe or a brew.

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Why correct gravity for temperature?

A hydrometer floats higher or lower depending on the density of the liquid, and a hot liquid is less dense. The instrument is graduated for a specific temperature, 20 °C for most models sold in Europe: at any other temperature, it is wrong.

The original gravity is often read on wort that is still warm, out of impatience. At 30 °C the error is 2.6 points; at 40 °C, nearly 6 points. That is enough to skew the calculated efficiency and the stated alcohol content.

The best option is still to cool the sample. When that is not possible, correct.

How is the correction calculated?

The correction is added to the gravity points read (SG × 1000):

corrected points = points read + 0.00352871 × (T − 20)² + 0.225225 × (T − 20)

where T is the sample temperature in °C. Above 20 °C the correction is positive, below it is negative.

The formula holds for a hydrometer calibrated at 20 °C. The calibration temperature is printed on the instrument or in its instructions.

Worked example

Values entered

  • Gravity read, as decimal SG: 1.048
  • Sample temperature in °C: 30

Result from the tool

Gravity corrected to 20 °C, in SG
1.051
Correction applied, in points (SG × 1000)
2.61

What the tool does not do

  • From 0 to 100 °C; above 60 °C the reading itself becomes unreliable and the hydrometer may crack.
  • For a hydrometer calibrated at 15.6 °C (60 °F), the correction is shifted by about 1 point.
  • The formula is established for water: the gap with a wort stays below the reading accuracy.

Frequently asked questions

At what temperature should I read the gravity?

At the calibration temperature of your hydrometer, most often 20 °C. Cool the sample in a glass of cold water for a few minutes: it is safer than a correction.

My hydrometer is calibrated at 15.6 °C, what should I do?

American models are calibrated at 60 °F, which is 15.6 °C. Read the sample at that temperature, or add about 1 point to readings taken at 20 °C.

And with the assistant?

Ask Krausi the same question in plain language: he picks this tool, does the calculation and files the result in your project.

I read 1.048 but the wort was still at 30 °C.

Corrected to 20 °C, your original gravity is 1.051 (+2.6 points). That is the value I'm logging in the brew.

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