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Plato Converter

Convert between degrees Plato, specific gravity, gravity points and Brix for brewing. Enter a reading, pick the scale you measured on and press Convert.

Written and reviewed by SM Arijul Islam · Last reviewed 21 October 2026 · Editorial standards · Report an error

About the Plato converter

Degrees Plato measure the extract in wort as a percentage by mass: 12 °P means 12 g of dissolved solids in every 100 g of wort. Home brewers usually measure specific gravity instead, so the two scales are constantly converted. This page uses the ASBC polynomial rather than the popular mental shortcut that one degree Plato is four gravity points, which drifts by 5% or more above 1.060.

Brix is included for refractometer users. A refractometer reads a sucrose solution, and wort is not pure sucrose, so a raw Brix reading runs about 4% high. That is the wort correction factor, and 1.04 is the usual starting point.

Formulas used

Specific gravity from Plato: SG = 1 + °P ÷ (258.6 − (°P ÷ 258.2) × 227.1)
Plato from specific gravity: °P = 135.997 × SG³ − 630.272 × SG² + 1111.14 × SG − 616.868
Gravity points: points = (SG − 1) × 1000
Brix from a refractometer: °Bx = °P × 1.04

Plato to gravity reference

Degrees Plato with the corresponding specific gravity and gravity points
Plato	Specific gravity	Gravity points	Typical beer
5 °P	1.0195	20	Session ale
8 °P	1.0318	32	Ordinary bitter
12 °P	1.0484	48	Standard lager and pale ale
15 °P	1.0611	61	IPA
18 °P	1.0740	74	Strong ale, bock
20 °P	1.0829	83	Barley wine, imperial stout
25 °P	1.1057	106	Very strong

Worked examples

A hydrometer reading of 1.048 is 12.0 °P, so about 12% of the wort by mass is extract.
A refractometer reading of 13 °Bx on unfermented wort corrects to 13 ÷ 1.04 = 12.5 °P, which is SG 1.050.
Gravity points 48 divided by 4 gives 12 — the quick rule, which is close at this strength.
At 1.090 the quick rule gives 22.5 °P but the polynomial gives 21.6 °P, a difference of nearly one degree.

Measuring Plato in the brewery

A hydrometer reads density directly: float it in the sample, read the specific gravity at the meniscus, and convert to Plato. A refractometer reads the refractive index of a drop, which correlates with dissolved solids — but only in a sugar solution containing no alcohol. Once fermentation has started, ethanol changes the refractive index and a raw refractometer reading drifts steadily away from the truth, so a correction based on the original gravity is needed.

The practical split most brewers settle on is a refractometer for quick readings before fermentation and for monitoring progress, and a hydrometer for the numbers that end up in the log. Both should be checked with distilled water at the temperature the instrument expects, usually 20 °C.

Two terms come up as soon as you compare beers. Original extract is the Plato of the wort before fermentation; apparent extract is the reading afterwards, which understates the true remaining extract because the alcohol present is less dense than water. Apparent attenuation is the share of the original extract that has been consumed:

Apparent attenuation % = (OE − AE) ÷ OE × 100

A 12 °P wort finishing at 2.5 °P has an apparent attenuation of 79 percent, a normal figure for an ale. Lagers often finish lower, and a fermentation that stalls well above the expected range is worth investigating before packaging.

Frequently asked questions

Is Plato the same as Brix?

Almost, and for brewing they are treated as the same scale. A refractometer reads a little high on wort, which is why the correction factor of about 1.04 is applied.

Why do gravity points work so well as a rule of thumb?

Because over the normal 5 to 15 °P range the relationship really is close to four points per degree. The approximation fails on imperial stouts and barley wines, and the error is always in the same direction.

Can I use these numbers after fermentation?

No. Alcohol is less dense than water, so a hydrometer reading on finished beer needs an alcohol correction. For a refractometer, a separate post-fermentation formula is required.

Does temperature matter?

Yes. Hydrometers are calibrated around 20 °C, and a sample 10 °C warmer reads roughly two points low, so cool the sample or apply a correction first.

What is 1.050 specific gravity in Plato?

A specific gravity of 1.050 is about 12.4 °P, or 50 gravity points. The converter uses the standard cubic approximation, so a hydrometer or refractometer reading may differ slightly.

Common mistakes to avoid

Trusting the multiply-by-four shortcut on high-gravity wort, where it overstates the extract.
Forgetting the wort correction factor and reading Brix as Plato.
Comparing a pre-fermentation figure with a post-fermentation one without an alcohol correction.
Recording a refractometer reading without noting whether it has been corrected — the two are easily confused later.