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.

Plato / Brix / Specific Gravity Converter

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.

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.
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.