Brix to Specific Gravity Converter

Two measurement scales dominate the world of fermentation: degrees Brix and specific gravity. Whether you are a home winemaker monitoring must sugar levels, a homebrewer tracking original gravity, or a cider maker assessing juice sweetness, understanding how these two scales relate to each other is fundamental to producing consistent, predictable results.

This converter handles the mathematics of Brix-to-SG and SG-to-Brix conversions using the polynomial approximations accepted across the brewing and winemaking industries. It also calculates three derived values — the Plato equivalent, the potential alcohol percentage assuming complete fermentation, and the estimated sugar content in grams per liter — giving you a comprehensive snapshot of your starting material in a single step.

What Is Brix?

Degrees Brix (°Bx) is a measure of the dissolved sugar content of an aqueous solution. One degree Brix equals one gram of sucrose per 100 grams of solution. In practice, fruit juice, grape must, and wort contain a mixture of sugars — glucose, fructose, maltose, and others — alongside non-sugar solutes such as acids, minerals, and proteins. A refractometer reads all dissolved solids, not only sugars, so Brix readings from real-world samples are approximate representations of sugar content rather than exact sucrose measurements.

In winemaking, the Brix of fresh grape juice is one of the most important quality indicators at harvest. Grapes destined for dry table wine are typically harvested at 21–25°Bx. Grapes for dessert wine or late-harvest styles may be picked at 28°Bx or higher. In homebrewing, Brix is sometimes used as an alternative to specific gravity, particularly by brewers who use refractometers instead of hydrometers.

What Is Specific Gravity?

Specific gravity (SG) is a dimensionless number that compares the density of a liquid to the density of pure water at the same temperature. Pure water has a specific gravity of exactly 1.000. A solution containing dissolved sugars is denser than water, so it has a specific gravity greater than 1.000. A wort with an original gravity (OG) of 1.055 is 5.5% denser than pure water at the reference temperature.

Specific gravity is the traditional measurement scale used in homebrewing. Hydrometers are the standard instrument for measuring it: you float the hydrometer in a sample tube and read the value from the graduated scale at the liquid surface. The scale is typically graduated in increments of 0.001 or 0.002. Most hydrometers are calibrated at 60°F (15.6°C) in the United States or 68°F (20°C) in Europe, requiring a temperature correction when the sample is measured at a different temperature.

The Conversion Formula

The relationship between Brix and specific gravity is nonlinear. At low sugar concentrations the two scales are nearly proportional, but at higher concentrations the relationship curves away from linearity. The formula used in this calculator is widely found in brewing software and reference texts:

For Brix to SG: SG = 1 + Brix / (258.6 − (Brix × 227.1 / 258.2)). This formula gives results accurate to within approximately ±0.001 SG over the Brix range typically encountered in brewing (0–35°Bx).

For the inverse conversion, SG to Brix, this calculator uses Newton's method to numerically invert the forward formula, ensuring exact consistency between both conversion directions.

Plato: The Brewing Industry Standard

Degrees Plato (°P) is the measurement scale used by professional breweries worldwide. Like Brix, Plato measures the weight of dissolved solids relative to the total solution weight, but it uses a slightly different reference table originally published by brewing scientist Fritz Plato in the early twentieth century. For practical purposes, Plato and Brix are numerically very close — the difference is less than 0.1°P across the range encountered in typical brewing applications.

The conversion from SG to Plato used in this calculator is: °P = −676.0672 + 1286.483 × SG − 800.172 × SG² + 190.0106 × SG³. This polynomial is widely cited in brewing chemistry texts and is the basis for the Plato scale used in modern laboratory instruments.

When reading yeast datasheets, recipe formulations from commercial breweries, or technical brewing publications, you will frequently encounter Plato rather than specific gravity. The converter on this page allows you to move freely between all three scales — Brix, SG, and Plato — from a single input.

Potential Alcohol

Potential alcohol is an estimate of the maximum alcohol by volume (ABV) that a fermenting liquid could theoretically produce if all fermentable sugars were consumed by yeast. This figure assumes complete fermentation down to a final gravity of approximately 1.000.

The calculation used here is derived from the standard homebrewing formula: Potential ABV = (SG − 1.000) × 131.25. This formula is an approximation; actual ABV after fermentation depends on yeast strain, fermentation conditions, temperature, and the proportion of fermentable versus non-fermentable sugars in the original wort or must.

In winemaking, a common rule of thumb is that each 1°Bx at harvest contributes roughly 0.55–0.60% potential ABV. A must at 22°Bx would therefore produce a wine of approximately 12–13% ABV, assuming nearly complete fermentation. In homebrewing, a wort at 1.055 OG would yield roughly 7.2% potential ABV under the same assumption.

Sugar Content in Grams per Liter

The sugar content estimate in g/L provides an intuitive sense of how much dissolved sugar is present in each liter of must or wort. The calculation is: sugar (g/L) ≈ Brix × SG × 10. This derives from the definition of Brix as grams per 100 grams of solution: multiplying by the density in kg/L (approximately equal to SG) and by 10 converts this to grams per liter.

For example, a grape must at 22°Bx with an SG of approximately 1.092 contains roughly 240 g/L of dissolved solids (primarily sugars). A typical table wine must might contain 200–250 g/L of sugar, while a dessert wine must might contain 300 g/L or more.

These figures are useful for recipe formulation, chapitalization calculations (adding sugar to boost potential alcohol), and understanding the fermentability of your starting material. Because Brix measures all dissolved solids rather than only sugars, the g/L figure should be understood as an approximation of the true fermentable sugar content.

Refractometers and Hydrometers

The two primary instruments for measuring Brix and specific gravity are the refractometer and the hydrometer. A refractometer measures how much a liquid bends (refracts) a beam of light; dissolved solids increase the refractive index, and the instrument reports this as a Brix reading. Refractometers require only a few drops of sample and give a result in seconds, making them popular for vineyard monitoring and quick checks during brewing.

Hydrometers measure density directly by floating in a sample. They require more sample volume than a refractometer but are not affected by the interference that dissolved carbon dioxide and ethanol can cause in refractometer readings. For this reason, refractometers are generally most reliable for measuring the original gravity of pre-fermentation samples; during and after fermentation, a hydrometer or a refractometer correction formula should be used.

Both instruments require temperature correction. Most hydrometers are calibrated at 60°F (15.6°C) or 68°F (20°C); corrections of approximately 0.001 SG per 4–5°C deviation are commonly applied. Refractometers are typically calibrated at 20°C. Using a digital refractometer with automatic temperature compensation reduces this source of error significantly.

Applications in Winemaking

In the winery, Brix monitoring begins long before harvest. Grape growers and winemakers sample berries regularly during the ripening period to track the progression of sugar accumulation and to choose the optimal harvest date. Commercial wineries typically use a combination of Brix, pH, and titratable acidity measurements to make this decision.

After crushing and pressing, the Brix of the must is measured again to determine whether chaptalization — the addition of sugar to increase potential alcohol — is necessary or permitted by local regulations. In cooler climates such as Burgundy or Germany, chaptalization is sometimes required in poor vintage years when grapes do not ripen fully. In warmer climates, the reverse problem of excess sugar sometimes necessitates the addition of water, where legally permitted.

Understanding the relationship between Brix, specific gravity, and potential alcohol allows winemakers to make informed decisions at every stage of production. The converter on this page provides all relevant derived values from a single measurement, reducing the need for multiple calculations.