Specific Gravity to Brix

How to Convert SG to Degrees Brix?

To convert specific gravity to degrees Brix, use the same polynomial as for Plato: °Bx = -616.868 + 1111.14 × SG - 630.272 × SG² + 135.997 × SG³. For practical brewing purposes, Brix and Plato are interchangeable. For example, SG 1.045 equals approximately 11.2°Bx. The Brix scale is most commonly encountered when using a refractometer, which is popular among homebrewers for its convenience — it requires only a drop of wort and gives an instant reading. This conversion matters most when you are moving between hydrometer-based recipes and refractometer-based brew day checks. Many brewers use a hydrometer for official OG and FG measurements but rely on a refractometer for mash runoff, pre-boil gravity, and kettle concentration because it wastes less wort and returns faster readings. Knowing how an SG target translates into Brix lets you compare instruments confidently and catch dilution or efficiency issues before the boil is over. It is also helpful when you are checking yeast starters, pilot batches, or split trials where sample size is too small to justify a full hydrometer jar.

How to Convert Specific Gravity to Degrees Brix

1. Take your specific gravity reading from a hydrometer.
2. Apply the polynomial formula, or use the quick estimate: °Bx ≈ (SG - 1) × 250.
3. The result is the sugar content in degrees Brix.
4. Note: if using a refractometer on fermenting beer, the alcohol will cause an incorrect reading — you must apply a correction formula.

Real-World Examples

History of Specific Gravity and Degrees Brix

The Brix scale was developed by Adolf Brix in the 19th century for the sugar industry. It measures the percentage of sucrose by weight in a solution and is the standard scale for refractometers used in agriculture (grape harvest, fruit juice production) and food science. Brewers adopted refractometers — and thus the Brix scale — because they offer faster readings than hydrometers and require much less sample volume.

Common Mistakes to Avoid

• Using a refractometer reading after fermentation has started without correcting for alcohol. Ethanol has a different refractive index than water, so a fermenting beer will show a falsely high Brix reading.
• Treating Brix and SG as having a simple linear relationship. While the approximation °Bx ≈ (SG - 1) × 250 works for typical brewing gravities, it is not exact.
• Skipping refractometer calibration with distilled water. If the instrument does not read 0°Bx in water, every SG-to-Brix comparison will be shifted and your brew day decisions may be wrong.
• Comparing a hot hydrometer reading to a cooled refractometer sample. Temperature affects both tools, so make sure the SG reading is corrected before you convert it to Brix.

Frequently Asked Questions