Brix Calculator: Convert Brix to Specific Gravity and Back

Brix ⇄ Specific Gravity Converter

Brix vs Specific Gravity: Two Rulers for the Same Sugar

Brix measures the mass percentage of dissolved sucrose: a 20 °Brix solution contains 20 grams of sugar per 100 grams of liquid. Specific gravity measures something different — density relative to pure water, which is defined as 1.000. A wort at SG 1.048 is 4.8% denser than water. Both scales track dissolved solids, so one converts to the other, which is exactly what the calculator above does. Who uses which is mostly tradition and tooling. Winemakers work in Brix because refractometers — which need only 2 or 3 drops of juice — are practical in a vineyard, and American wine grapes are typically picked between 22 and 26 °Brix. Brewers work in specific gravity because hydrometers read SG directly, and every standard recipe lists an original gravity (say 1.048) and a final gravity (say 1.010); ABV formulas, attenuation math, and priming calculations are all built on gravity points. Neither scale is more accurate — they’re different rulers for the same sugar. The one wrinkle: both instruments actually respond to all dissolved solids, including proteins, acids, and dextrins, not just fermentable sugar, which is why beer wort needs the correction factor covered below.

The Conversion Math, With Worked Examples

The calculator above uses two standard formulas. Brix to SG: SG = 1 + (Brix ÷ (258.6 − (Brix ÷ 258.2) × 227.1)). Plug in 12 °Brix: the denominator is 258.6 − (12 ÷ 258.2) × 227.1 = 248.05, and 12 ÷ 248.05 = 0.0484, so SG ≈ 1.048. SG to Brix runs through the cubic approximation Brix = 143.254×SG³ − 648.670×SG² + 1125.805×SG − 620.389; feed it 1.048 and you get 11.9 °Brix, so the two formulas round-trip within about 0.1 °Brix across the normal fermentation range. More anchor points worth memorizing: 10 °Brix ≈ 1.040, 20 °Brix ≈ 1.083, and 25 °Brix ≈ 1.106. For quick mental math, multiply Brix by 4 to get gravity points — 12 × 4 = 48, meaning 1.048. That shortcut stays within about a point up to roughly 15 °Brix, then starts underestimating: 20 °Brix is really 1.083, not 1.080. When the difference matters — calculating ABV or hitting a target original gravity — use the full formula in the calculator rather than the ×4 rule.

The Wort Correction Factor (Default 1.040)

Refractometers are calibrated against sucrose solutions, but beer wort’s sugar is mostly maltose and maltotriose plus unfermentable dextrins, and those molecules bend light slightly differently than table sugar. The net effect: wort reads roughly 4% high on the Brix scale. The fix is the wort correction factor (WCF) — divide the raw refractometer reading by it before converting, which the calculator above does automatically. It defaults to 1.040, the value most homebrew software uses. Example: a raw reading of 13.0 °Brix ÷ 1.040 = 12.5 corrected °Brix, which converts to SG 1.050. Skip the correction and you’d log about 1.053 — two gravity points high, enough to overstate a 5% beer’s ABV by roughly 0.3%. Real-world WCFs run from about 1.02 to 1.06 depending on the instrument, the grain bill, and the recipe. To find yours, measure the same unfermented wort with both a hydrometer and a refractometer on 3 or 4 brew days, convert each hydrometer SG to Brix, divide the refractometer reading by that number, and average the results. If you’d rather not bother, 1.040 lands within a gravity point for most pale worts.

Why Alcohol Breaks Refractometer Readings

A refractometer reading is only a true Brix value while the liquid is unfermented. Once yeast starts converting sugar to ethanol, the reading becomes a blend of two opposing signals: residual sugar, which raises the refractive index, and alcohol, which also bends light strongly — ethanol’s refractive index is about 1.361 versus 1.333 for water — while simultaneously lowering the liquid’s density. The two scales diverge, and the raw number no longer means percent sugar. The classic trap: a beer that started at 1.050 and finished at a true 1.010 will still read around 6 °Brix on a refractometer. Naively converted, that’s SG 1.024, which would suggest a stuck fermentation that isn’t actually happening. Correction formulas exist — they take your original gravity plus the current refractometer reading and back-calculate an estimated gravity — but they’re typically only accurate to within about 0.002 SG. That’s fine for watching fermentation trend downward day to day, but not for the final gravity you’ll plug into an ABV calculation. The standard homebrew practice: use the refractometer on brew day and during active fermentation for trend-watching, then confirm final gravity with a hydrometer, which reads density directly and doesn’t care how much alcohol is present.

Brix in Wine and Cider: Potential Alcohol

Winemakers and cidermakers live on the Brix scale because the key harvest decision is sugar ripeness. American wine grapes are typically picked between 22 and 26 °Brix, with around 24 °Brix common for dry table wines. Potential alcohol is estimated as Brix × 0.55 to 0.60, with 0.59 the most widely used single factor; the true yield depends on yeast strain and how completely the must ferments. At 24 °Brix, that range predicts roughly 13.2% to 14.4% ABV, with the 0.59 factor giving 14.2%. Cider runs much lower: fresh apple juice usually measures 10 to 15 °Brix, for a potential 5.5% to 8.5% ABV. One convenient difference from beer: grape and apple sugars are glucose and fructose, which refract close enough to sucrose that no wort-style correction is needed — read the juice straight and leave the calculator’s correction factor at 1.000. The alcohol limitation still applies in full, though. Once the must starts fermenting, refractometer Brix is no longer valid, so wine and cider makers switch to a hydrometer to track fermentation and confirm dryness — a finished dry wine typically reads SG 0.990 to 0.996, below water, because alcohol is lighter than water.

Refractometer or Hydrometer: A Practical Workflow

For US homebrewers — federal law (26 U.S.C. §5053) has allowed home beer production since 1978, up to 100 gallons per year in a one-adult household and 200 gallons with two or more adults — the practical answer is to own both instruments. The refractometer wins on brew day and at harvest: it needs 2 or 3 drops, reads in seconds, and most models under $40 include automatic temperature compensation (ATC) that self-corrects between about 50°F and 86°F. The hydrometer wins once fermentation starts: it reads density directly, is immune to the alcohol problem, and is the only reliable way to confirm final gravity. Its drawbacks are the sample size — typically 100 mL or more — and its fixed calibration temperature, usually 60°F or 68°F, so warm samples read low; an 80°F sample on a 60°F hydrometer reads about 2 gravity points under. A sensible workflow: refractometer for mash and pre-boil checks and the original gravity reading (with the 1.040 wort correction applied in the calculator above), hydrometer for fermentation tracking and final gravity, then both numbers into an ABV calculation. If your hydrometer sample is warm, run it through a temperature correction first.