Brix Calculator
Convert degrees Brix into specific gravity, sugar content and potential alcohol using USDA and OIV tables.
What it does
Degrees Brix is the standard way to talk about how much sugar is dissolved in a liquid. A reading of 12.5 °Bx means 12.5 grams of sugar in every 100 grams of solution, which is the definition the International Organisation of Vine and Wine uses in its refractometer method.
Two different tables are needed to answer most questions about a Brix reading. The USDA sugar conversion table covers pure sucrose solutions and gives the apparent specific gravity at 20/20 °C, the refractive index at 20 °C, and the weight of solids in a US gallon. The OIV method covers grape must and adds the density of the must, the sugar per liter and per kilogram, and the potential alcohol.
A must and a plain sugar solution with the same Brix reading are not the same liquid. Must contains other things that change its density and its sugar content, which is why the OIV numbers for 12.5 °Bx give 108.9 g of sugar per liter while the sucrose table gives about 131 g per liter of pure solution.
Potential alcohol is the alcohol a fermenting yeast would produce if every gram of sugar were converted. It is an estimate made before fermentation, not a promise about the finished wine, since real fermentations leave some sugar behind and produce other compounds as well.
Refractometers are calibrated on a sucrose scale, so a reading taken from juice or wine is a sucrose equivalent. The difference between that reading and the true sugar content is small for wine and larger for juice with its own sugars, so treat refractometer numbers for juice as an approximation.
How to use
- Pick metric or imperial for the sugar content.
- Enter the Brix reading from your refractometer.
- Read the specific gravity and the refractive index for the sucrose solution.
- Read the sugar per liter or per US gallon.
- If the reading is between 10 and 74.9 °Bx, read the must density, must sugar and potential alcohol.
- Use the potential alcohol as a planning number, then ferment and measure the real alcohol.
Formula
- °Bx
- Degrees Brix, grams of sugar per 100 grams of solution.
- SG
- Apparent specific gravity at 20/20 °C from the USDA sucrose table.
- RI
- Refractive index at 20 °C from the same table.
- Must sugar
- Grams of sugar per liter of grape must from the OIV table.
- Potential alcohol
- Percent alcohol by volume the sugar could produce at 20 °C.
The tables are read at 20 °C, so a warm or cold sample gives a slightly different refractometer reading. The USDA apparent specific gravity is stated at 20/20 °C, which means the density of the sample compared with water at the same temperature. The Baume scale that some older tools still use is not included here, because it needs a specific gravity measured at 60/60 °F and mixing the two conventions produces a wrong answer.
Worked example
Example: a must at 12.5 °Bx
Defaults: metric units, 12.5 degrees Brix.
- USDA sucrose table at 12.5 °Bx: apparent specific gravity 1.05047, refractive index 1.35171 at 20 °C.
- USDA solids figure: 1.093 lb of sugar solids in one US gallon of solution.
- Convert to metric: 1.093 x 453.59237 / 3.785411784 = 131.0 g per liter.
- OIV table at 12.5 °Bx: must density 1.0493 g/mL at 20 °C.
- OIV must sugar: 108.9 g per liter, and 103.8 g per kilogram.
- OIV potential alcohol: 6.47% by volume.
- The tool shows 1.05047, 1.35170, 131.0 g per liter, 1.0493 g/mL, 108.9 g/L and 6.47%.
Reference table
| Degrees Brix | Specific gravity | Must sugar | Potential alcohol |
|---|---|---|---|
| 10.0 | 1.04003 | 82.2 g/L | 4.89% |
| 12.5 | 1.05047 | 108.9 g/L | 6.47% |
| 14.0 | 1.05683 | 125.2 g/L | 7.44% |
| 16.0 | 1.06542 | 147.1 g/L | 8.74% |
| 18.0 | 1.07413 | 169.4 g/L | 10.07% |
| 20.0 | 1.08297 | 191.9 g/L | 11.40% |
| 22.0 | 1.09194 | 214.7 g/L | 12.76% |
| 24.0 | 1.10104 | 237.8 g/L | 14.13% |
Limits
- The must rows only run from 10.0 to 74.9 °Bx, so lower readings show as not tabulated.
- Refractometer readings are on a sucrose scale, so a liquid with its own sugars does not read exactly right.
- Tables are published at 20 °C, and a sample at a different temperature needs a correction.
- Potential alcohol is a planning figure that ignores how much sugar the yeast leaves behind.
Common mistakes
- Reading Brix as grams per liter instead of grams per 100 grams of solution.
- Applying the must numbers to a plain sugar solution, or the sucrose numbers to must and expecting them to match.
- Treating the specific gravity of a must as the specific gravity of the finished wine, since alcohol changes it.
- Using a potential alcohol figure as the alcohol on the label.
- Skipping the temperature correction on a hot sample, which pushes the reading high.
Try it yourself
Quick checks. Answers sit tucked under each question.
A must reads 16 °Bx. What does the tool give?
Specific gravity 1.06542, refractive index 1.35730 at 20 °C, 170.0 g of sugar per liter in a sucrose solution, 147.1 g per liter of must, and a potential alcohol of 8.74%.
How much sugar is in a 750 mL bottle of must at 12.5 °Bx?
The OIV table gives 108.9 g per liter, so a 0.75 liter bottle holds 108.9 x 0.75 = 81.7 g of sugar.
A juice reads 7 °Bx. Which outputs are available?
The specific gravity 1.02773 and the refractive index 1.34320 come from the sucrose table, along with 71.8 g of solids per liter. The must density, must sugar and potential alcohol read as not tabulated below 10 °Bx.
Questions
What does one degree Brix mean?
One gram of sugar per 100 grams of solution. It is a mass percentage, so the volume of the liquid does not enter into it.
Is degrees Brix the same as sugar by volume?
No. Brix is by mass, and weight by volume is a different thing. Converting between them needs the density of the solution, which is why the tables list density next to the sugar content.
How do I convert Brix to specific gravity?
Read the USDA sucrose table. At 12.5 °Bx the apparent specific gravity at 20/20 °C is 1.05047, at 16 °Bx it is 1.06542, and at 20 °Bx it is 1.08297.
What is potential alcohol?
The alcohol by volume that the sugar in the liquid could turn into if a ferment went all the way. It is read from the OIV table and is an estimate before fermentation.
Why do my two tables give different sugar per liter for the same Brix?
The USDA table describes a pure sucrose solution, while the OIV table describes grape must, which has other components and a different density. Both are correct for their own liquid.
Does Brix tell me the alcohol in my finished wine?
No. Once fermentation starts, the sugar disappears and the alcohol replaces it, so the reading drops. Measure the finished alcohol directly instead.
Sources
- USDA Agricultural Marketing Service: Appendix XV, Sucrose Conversion Table
- International Organisation of Vine and Wine: method OIV-MA-AS2-02 for sugar in musts
- OIML Recommendation R 124: refractometers for measuring sugar content in grape musts