Brix to Specific Gravity / Plato Converter

What Brix, Plato, and Specific Gravity Actually Measure

Brix, Plato, and specific gravity are three different ways of answering the same basic question: how much sugar is dissolved in this liquid? Winemakers, brewers, and juice producers all need this number, but each corner of the industry grew up using a different scale, which is exactly why converters like this one exist.

Degrees Brix (°Bx) measures the percentage of sucrose by weight in a solution, read most often with a handheld refractometer by placing a couple of drops of juice or wort on the prism and looking through the eyepiece. Degrees Plato (°P) is the brewing industry's own version of the same idea, built on very similar reference tables. In practice, Brix and Plato are close enough to be treated as interchangeable to three decimal places, which is why most brewing software and calculators — including this one — use a single conversion for both.

Specific gravity (SG) takes a completely different approach: instead of estimating sugar content directly, it compares the density of your liquid to the density of plain water. Water measures exactly 1.000 SG, and because dissolved sugar makes a liquid denser than water, a sugary must, wort, or juice always reads above 1.000. A hydrometer measures SG directly by floating in the liquid, while a refractometer measures Brix or Plato and this calculator converts that reading into the equivalent SG for you.

How to Convert Brix or Plato to Specific Gravity

This calculator uses the ASBC polynomial (De Clerck, 1957), the same reference formula found in official American Society of Brewing Chemists tables. It's accurate to within about ±0.0001 SG across the 0-30°Bx range that covers virtually every beer, wine, cider, or mead you'll ever measure, which makes it far more precise than the simple 'divide by four' shortcuts some brewers use for a rough estimate.

Just type in your Brix or Plato reading and the calculator instantly returns the matching specific gravity, along with the equivalent Baumé reading — a third hydrometer scale still used in some winemaking and industrial contexts, especially in Europe. If you only have a refractometer and your recipe or fermentation software asks for an SG figure, this is the conversion you need before pitching yeast or logging your original gravity.

How to Convert Specific Gravity Back to Brix or Plato

Sometimes the conversion needs to run the other way — you've got a hydrometer reading in SG, but a recipe, a wine kit, or a piece of software wants the equivalent Brix or Plato figure. This calculator handles that with the standard cubic inverse formula, giving you an accurate Brix/Plato equivalent for any SG reading between roughly 1.000 and 1.150, which comfortably covers everything from a light table wine must to a high-gravity barleywine or barrel-aged strong ale.

Why a Refractometer Lies to You After Fermentation Starts

A refractometer works by measuring how much dissolved solids bend light passing through your sample. Before fermentation, sugar is essentially the only thing in the liquid affecting that bend, so a raw Brix reading is highly accurate. The moment yeast starts converting sugar into alcohol, though, the picture changes: alcohol bends light differently than sugar does, and it bends it in a way that makes the refractometer under-read how much the gravity has actually dropped. In plain terms, your refractometer will show a Brix number that looks higher than the beer, wine, or cider's true remaining gravity, making it seem like fermentation has barely progressed when it may already be nearly finished.

This is the single most common point of confusion for new brewers using a refractometer instead of a hydrometer. Without correcting for it, you'll consistently underestimate how much your gravity has dropped and underestimate your final ABV — sometimes by a meaningful margin on stronger beers and wines.

The Sean Terrill Correction Formula, Explained Simply

Homebrewer Sean Terrill solved this problem by comparing thousands of paired refractometer and hydrometer readings and fitting a cubic formula that reliably backs out the true final gravity from two numbers you already have: your Original Brix reading (taken before pitching yeast, when the refractometer is still fully accurate) and your Final or current Brix reading (taken any time during or after fermentation). It's widely regarded as the most reliable refractometer correction method available, and it's the same formula most homebrewing apps and calculators use under the hood.

Enter both readings into the Refractometer Correction mode above and the calculator returns your corrected final gravity in both SG and Brix, your apparent attenuation (how much of the available sugar the yeast actually consumed), and an estimated ABV using the standard (OG − FG) × 131.25 formula. The correction is most accurate once fermentation is well underway, generally above about 60% apparent attenuation — early in fermentation, when very little sugar has converted yet, any correction formula has less to work with and the numbers carry more uncertainty.

What Is the Wort Correction Factor (WCF)?

Wort, must, and juice aren't pure sugar water — they also contain proteins, minerals, tannins, and other dissolved compounds that bend light slightly differently than a pure sucrose solution does. Most refractometers, however, are factory-calibrated using pure sucrose solutions. The Wort Correction Factor (WCF) is a small adjustment, typically somewhere around 1.00 to 1.04, that some refractometer manufacturers and brewers apply to their Brix readings before running the Terrill correction, to account for that difference.

If your refractometer's manual doesn't mention a specific WCF, leave this field at 1.00 and use the standard, unmodified Terrill formula — it's accurate for the vast majority of home and craft brewing situations. Only adjust it if you've calibrated your specific instrument against a hydrometer and found a consistent, repeatable offset worth correcting for.

Refractometer vs. Hydrometer: Which Should You Trust?

Both instruments measure the same underlying thing, but they have different strengths. A refractometer needs only two or three drops of liquid, gives an instant reading, and isn't affected by temperature the way an uncorrected hydrometer is, which makes it fantastic for checking original gravity on brew day or tracking a fermentation's progress without wasting sample volume. Its one real weakness is exactly the alcohol-interference problem this calculator corrects for.

A hydrometer, on the other hand, reads specific gravity directly and doesn't need any alcohol correction at any stage of fermentation, but it requires a much larger sample, takes longer to settle to an accurate reading, and its reading does need a small temperature correction if your sample isn't at the calibration temperature stamped on the instrument (usually 60°F/15.6°C or 68°F/20°C). Many brewers use both: a refractometer for quick daily checks, and a hydrometer to confirm the true final gravity right before bottling or kegging, since getting that number wrong risks bottle bombs from underestimated fermentable sugar.

Typical Brix and Gravity Ranges by Beverage

Different beverages start and finish in very different ranges, which is useful context when you're checking whether a reading looks reasonable.

• Session beer wort: 8-11°Bx (SG ~1.032-1.044)
• Standard ale/lager wort: 11-15°Bx (SG ~1.044-1.062)
• High-gravity beer (barleywine, imperial stout): 18-28°Bx (SG ~1.074-1.120)
• Wine grape must at harvest: 19-25°Bx (SG ~1.080-1.106)
• Cider apple juice: 10-15°Bx (SG ~1.040-1.062)
• Mead honey must: 24-35°Bx (SG ~1.100-1.150+)

Who Uses This Converter

Homebrewers use the Brix-to-SG conversion constantly on brew day to log an original gravity from a quick refractometer sample, and lean on the refractometer correction mode throughout fermentation to track progress without wasting large samples on a hydrometer. Winemakers and cidermakers use Brix readings straight from the vineyard or press to judge harvest timing and estimate potential alcohol before fermentation even starts. Mead makers, who often work with very high starting gravities, use the SG-to-Brix conversion to cross-check honey-must recipes against target readings.

Juice and food producers use Brix as a standard quality and ripeness metric on production lines, since it's a fast, non-destructive way to check sugar content without lab equipment. Whatever the use case, this converter turns any one of the three common readings — Brix, Plato, or specific gravity — into the others in a couple of seconds, and handles the trickier alcohol-correction math that trips up most brewers using refractometers for the first time.

A Quick Note on Accuracy

The formulas used here are the same reference polynomials and correction methods relied on throughout the brewing and winemaking world, and they're accurate enough for recipe planning, fermentation tracking, and quality checks. That said, refractometers and hydrometers are precision instruments — make sure yours is calibrated with distilled water (which should read exactly 0°Bx or 1.000 SG) and, for hydrometers, take readings at or near the calibration temperature printed on the instrument, since temperature swings alone can shift a reading noticeably.

For any decision where getting the number wrong has real consequences — like confirming a beer or cider has truly finished fermenting before bottling — cross-check a refractometer-based estimate against a hydrometer reading taken directly, rather than relying on a correction formula alone.