How do you convert specific gravity to degrees Plato?

This tool uses the ASBC cubic polynomial: Plato = -616.868 + 1111.14 x SG - 630.272 x SG^2 + 135.997 x SG^3. It is accurate across the normal brewing range and is the standard formula used by professional brewers.

Are Brix and Plato the same thing?

They are very close but defined against slightly different reference substances. Brix is based on sucrose and Plato on a maltose-equivalent sugar, so they diverge by less than 0.1 degrees in the brewing range. Many brewers treat them as interchangeable, and this tool does too unless you need lab precision.

Why is my refractometer reading off after fermentation?

Refractometers read Brix accurately only in wort with no alcohol. Once fermentation starts, alcohol skews the refractive index, so a finished-beer Brix reading needs a separate alcohol-correction formula and will not match a hydrometer here.

What specific gravity does 12 degrees Plato equal?

Roughly 1.048. A common rule of thumb is that each degree Plato is about 4 gravity points, so 12 Plato is near 1.048 and 20 Plato is near 1.083. The polynomial gives the exact figure.

Does this work for wine and cider too?

Yes. Winemakers and cider makers often measure in Brix, and the same gravity relationship applies. Enter your Brix or SG reading and the tool converts it just as it does for beer wort.

What is the Plato / Brix / Specific Gravity Converter?

Bidirectional converter between degrees Plato, Brix, and specific gravity for brewing and winemaking. Uses the ASBC polynomial formula for accurate gravity-to-Plato conversion and shows working. Runs 100% in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Plato / Brix / Specific Gravity Converter

Name: Plato / Brix / Specific Gravity Converter
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This converter moves freely between the three gravity scales brewers and winemakers use most: degrees Plato, Brix, and specific gravity. Enter a reading in any one scale and the other two appear instantly, with the working shown so you can trust the numbers.

How it works

Specific gravity (SG) is the ratio of the density of your liquid to the density of water. Plato and Brix express the same dissolved-sugar content as a percentage by mass. The tool uses the industry-standard ASBC cubic polynomial to go from SG to Plato:

Plato = -616.868 + 1111.14 x SG - 630.272 x SG^2 + 135.997 x SG^3

Going the other way, from Plato to SG, a widely used inverse approximation is:

SG = 1 + (Plato / (258.6 - (Plato / 258.2) x 227.1))

Brix and Plato are treated as numerically interchangeable here, since they differ by less than 0.1 degrees in the brewing and winemaking range. If you have a Brix reading from a refractometer, that is effectively your Plato value for recipe purposes.

Worked example

Say your hydrometer reads 1.048. Plugging into the polynomial:

1111.14 x 1.048 = 1164.48
-630.272 x 1.048^2 = -692.18
135.997 x 1.048^3 = 156.58
Sum with the constant: about 12.0 degrees Plato.

So 1.048 SG equals roughly 12 °Plato / 12 °Brix — a typical strength for a standard-gravity ale.

When each scale appears in practice

Degrees Plato is the professional brewing standard. German brewing law, the ASBC Beer Analysis Methods, and most commercial craft breweries express original and final gravity in °P. Equipment such as inline density meters and Anton Paar instruments typically output in Plato.

Brix dominates in winemaking and cider production. The Brix scale is defined against pure sucrose solutions, which is close enough to grape must or apple juice for practical use. Most winemaking refractometers are graduated in Brix.

Specific gravity is the traditional home-brewer scale, read from a floating glass hydrometer. A reading of 1.050 means the liquid is 5% denser than water, and “50 gravity points” is a common shorthand.

Attenuation and alcohol calculation

One key reason brewers convert between scales is to calculate attenuation and estimated alcohol content. If your original gravity is 1.056 (about 13.9 °P) and your final gravity is 1.010 (about 2.6 °P), apparent attenuation is roughly (13.9 − 2.6) / 13.9 ≈ 81%. Alcohol by volume is approximately (OG − FG) × 131.25, or about 6.0% in this example. The tool gives you both SG values so you can plug them straight into attenuation and ABV formulas.

Tips and notes

Use the full SG form (for example 1.052), not the points-only shorthand (52), so the polynomial receives the correct magnitude.
Refractometers read Brix and are perfect for pre-fermentation wort, but alcohol distorts the reading once fermentation begins — switch to a hydrometer for finished gravity.
Temperature matters: a standard hydrometer is calibrated at 20°C (68°F). Hot wort fresh from the kettle reads artificially low; cool to room temperature or apply a temperature correction before converting.
For lab-grade work the tiny Brix-versus-Plato difference matters; for everyday brewing it does not. Every calculation here runs locally in your browser.