Gravity scales explained
Brewers, winemakers and mead makers all measure the same thing, how much sugar is dissolved in the liquid, but they use different scales:
- Specific gravity (SG) compares the liquid's density with water (1.000). Homebrewers in North America mostly use it, with hydrometers reading in SG.
- Brix (°Bx) is the percentage of sugar by weight. Winemakers and refractometers use it.
- Plato (°P) is the brewing equivalent of Brix, and close enough to treat them as the same.
- Baumé (°Bé) is used in French and Australian winemaking, and roughly equals potential alcohol.
Formulas
The converter uses the standard brewing formulas:
SG = 1 + Brix / (258.6 − (Brix / 258.2 × 227.1))
Brix = −463.37 + 668.72·SG − 205.35·SG²
Baumé = 145 − 145 / SG
Quick reference
| Brix |
SG |
Baumé |
Potential ABV (to 0.996) |
| 10 |
1.040 |
5.6 |
5.7% |
| 15 |
1.061 |
8.4 |
8.7% |
| 20 |
1.083 |
11.1 |
12.0% |
| 22 |
1.092 |
12.2 |
13.4% |
| 25 |
1.106 |
13.9 |
15.6% |
| 30 |
1.129 |
16.6 |
19.7% |
Reading from a refractometer partway through fermentation? Raw Brix readings are skewed by alcohol, so use the refractometer calculator instead. To turn readings into alcohol content, use the ABV calculator or the wine ABV calculator.
Method and sources
- Brix and Plato: converted from gravity with a standard brewing polynomial. We checked it against the reference polynomial below, and the two agree within 0.1 °Bx between 1.000 and 1.140.
- Baumé: °Bé = 145 − 145 / SG, the standard scale for liquids heavier than water.
- Sugar in g/L: about 2.6 g per liter per gravity point. That follows from the Brix definition (grams of sucrose per 100 g of solution) times the solution's density, and holds between 2.59 and 2.62 from 1.020 to 1.120. Grape must also contains acids and other solids that raise gravity, so its real sugar content runs a little lower.
- Potential ABV: Hall's alternate equation, assuming the wine ferments dry to 0.996.
Sources
Frequently asked questions
How do I convert Brix to specific gravity?
SG = 1 + Brix / (258.6 - (Brix / 258.2 x 227.1)). For example, 20 °Brix is about 1.083. This converter does the arithmetic for you in both directions.
Are Brix and Plato the same?
Almost. Both measure sugar as a percentage by weight, and they differ only in the third decimal place, so brewers and winemakers treat them as interchangeable.
What is Baumé?
Baumé is a density scale used in French and Australian winemaking. One degree Baumé roughly equals 1% potential alcohol, which makes it handy for judging grape ripeness.