How to use the brix, plato and specific gravity converter
- Choose which scale your reading is on: specific gravity, degrees Plato or degrees Brix.
- Enter the reading. Specific gravity runs from 1.000 to 1.200, and Plato or Brix from 0 to 45.
- Read the other two scales and the gravity points in the summary and in the table.
- Use the specific gravity result in other brewing tools, or compare the Plato value with a recipe that lists it.
Formula
SG = 1 + P / (258.6 - (P / 258.2) x 227.1)
P = 258.6 x (SG - 1) / (1 + (SG - 1) x 227.1 / 258.2)
gravity points = (SG - 1) x 1000
for wort and juice, degrees Brix = degrees Plato
Both scales state grams of dissolved sugar in 100 grams of solution. The two formulas are exact inverses of each other, so converting there and back gives the number you started with.
Two readings in each direction
A wort at 12 degrees Plato has SG = 1 + 12 / (258.6 - 0.04648 x 227.1) = 1 + 12 / 248.05 = 1.0484, which is 48.4 gravity points. A wort at 1.050 is 0.05 above water, so P = 258.6 x 0.05 / (1 + 0.05 x 0.8796) = 12.93 / 1.04398 = 12.39 degrees Plato.
Juice read at 18 degrees Brix has a specific gravity of 1.0741. The tool also checks itself against a separate published polynomial for Plato: across the range from 1.0025 up to 1.12 the two agree within 0.01 degree.
What the three scales measure
Specific gravity compares the density of a liquid with water. Plato and Brix give the same idea as a percentage of sugar by weight, so 12 degrees means about 12 grams of sugar-like extract in each 100 grams of wort. Brewers often see Plato in recipes and specific gravity on a hydrometer, while growers and winemakers read Brix on a refractometer.
For planning a batch, take the specific gravity from here to the Gravity Dilution and Boil-Off Calculator, or estimate the alcohol of the finished beer with the ABV Calculator.
Why fermenting samples are different
A refractometer measures how light bends. Alcohol bends it differently from sugar, so a reading of beer or must that has started to ferment needs a correction that depends on the instrument and the starting gravity. This tool does not apply one. For anything that has begun to ferment, use a hydrometer and correct it for temperature.
Assumptions and limits
- The liquid is unfermented and its dissolved solids behave like sucrose.
- Plato and Brix are treated as the same number, which is how brewers and winemakers use them for wort, must and juice.
- The specific gravity is measured at the temperature the instrument was made for, or has already been corrected.
- Values are rounded for display only, and the formulas run on unrounded numbers.
Frequently asked questions
Is Brix exactly the same as Plato?
They come from slightly different sucrose tables, but the difference is far smaller than the reading error of a hydrometer or refractometer. For practical use the two are treated as equal.
What are gravity points?
Points are the part of specific gravity after the decimal point multiplied by 1000. A gravity of 1.048 is 48 points, which makes it easy to add and scale amounts of sugar by hand.
Can I use this for a sugar solution that is not wort?
It works for plain sugar water, juice and most wort. Liquids with a lot of salt, alcohol or other dissolved solids do not follow the sucrose table, so the numbers will be off.
Why does the tool ask for a range of 1.000 to 1.200?
Beyond that range the relation between density and sugar is less well known and the fitted formula is no longer a safe guide, so the tool asks you to check the reading.