A Free Calculator · Homebrew & Winemaking · Updated 2026
Convert Brix to specific gravity — and understand what the number means
A refractometer gives you Brix. Your recipe calls for an original gravity. This
calculator closes the gap: enter your unfermented wort or must reading and get
specific gravity (SG) and gravity points instantly. The formula is shown in full,
and the one caveat that trips up many homebrewers — why you cannot use this
conversion once alcohol is present — is explained directly.
SG to 3 decimal places·Gravity points·Pre-fermentation only
Pre-fermentation readings only
This conversion is accurate only for unfermented wort or must — where the liquid
contains sugar but no alcohol. Once fermentation starts, alcohol changes how a
refractometer bends light and the reading runs high. A mid-fermentation
or post-fermentation Brix reading fed into this calculator will overstate your
specific gravity. Use a hydrometer for final gravity, or apply a dedicated
refractometer-correction formula that accounts for alcohol content.
Enter your refractometer reading in degrees Brix. The calculator returns specific gravity and gravity points using the standard three-constant polynomial formula. Valid for unfermented wort, must, or any sugar-water solution with no alcohol present.
Your refractometer reading
°Bx
Valid range 0–40 °Bx. Most homebrew beer wort falls between 8 and 20 °Bx;
wine must is typically 18–26 °Bx.
Specific gravity:
Specific gravity (SG)
Density relative to water (1.000). A hydrometer reads this directly.
Gravity points
SG expressed as an integer — easier for blend arithmetic and brewing software.
Brix entered
Your refractometer reading, confirmed.
The formulas, in full
Nothing here is a black box. These are the exact calculations the tool runs — the same
arithmetic you could do on a calculator or a piece of paper. The named constants
(A, B, C) come from the standard three-constant polynomial used throughout the
brewery and food-science literature.
How each number is derived
Constants (standard three-constant polynomial)
A = 258.6 (denominator offset)
B = 258.2 (Brix scaling divisor)
C = 227.1 (Brix scaling multiplier)
1 — Specific gravity from Brix
inner = (Brix ÷ B) × C
denom = A − inner
SG = 1 + (Brix ÷ denom)
Example at 12 °Bx:
inner = (12 ÷ 258.2) × 227.1 = 10.5546
denom = 258.6 − 10.5546 = 248.045
SG = 1 + (12 ÷ 248.045) = 1.048
2 — Gravity points from SG
gravity_points = (SG − 1) × 1000
Example at SG 1.048:
gravity_points = (1.048 − 1) × 1000 = 48
Brix → SG quick reference
Common Brix readings with their corresponding SG and gravity points, calculated
from the same three-constant formula above. Use this as a sanity check against
your own reading.
Brix (°Bx)
Specific gravity (SG)
Gravity points
Typical use
5 °Bx
1.020
20
Very light session beer; some low-sugar kombucha starts
10 °Bx
1.040
40
Pale ale or lager range; light cider must
12 °Bx
1.048
48
Standard American ale; hop-forward IPA low end
15 °Bx
1.060
60
IPA, stout, amber ale; dry table wine must lower range
20 °Bx
1.082
82
Strong ale; fresh grape must mid-range; mead starting point
SG and gravity point values calculated from the three-constant polynomial (A = 258.6,
B = 258.2, C = 227.1). Figures rounded to 3 decimal places / whole points.
Actual gravity depends on your specific wort composition — treat these as reference
points, not guarantees.
Why a refractometer needs special handling once fermentation starts
The single most important thing to understand about using a refractometer in
brewing is that it works correctly only before alcohol enters the picture.
The physics: alcohol bends light differently than sugar does
A refractometer measures the refractive index of a liquid — how sharply it bends a beam of light. The Brix scale maps refractive index to sugar concentration, but that mapping was built for pure sugar-water solutions. Ethanol has a refractive index roughly 1.36, compared to water's 1.33 and sucrose solution's 1.34–1.50 depending on concentration. Once your wort begins fermenting, the alcohol that forms pulls the refractive index in a different direction than sugar alone would. The instrument cannot distinguish between "a lot of sugar" and "some sugar plus some alcohol" — it averages the optical effect and reports a Brix reading that is too high.
What "reading too high" means in practice
Suppose your original gravity was 1.052 (13 °Bx). Midway through fermentation, you check with the refractometer and it reads 10 °Bx — which this calculator would convert to SG 1.040. In reality, the alcohol present is artificially inflating the reading; the true SG might be closer to 1.025. Relying on the uncorrected refractometer reading would cause you to pull beer off the yeast too early, believing fermentation is further from complete than it actually is.
The right tool for each stage
Before pitching yeast, a refractometer is fast and accurate — a single drop from the kettle is all it needs, and no temperature correction is required with an ATC model. After fermentation begins, switch to a hydrometer: it measures true density directly and is not confused by alcohol. If you want to continue using a refractometer during and after fermentation, a separate refractometer-correction formula — typically the Sean Terrill or Bonham equation — is required to back out the alcohol contribution. That correction is not built into this calculator because it requires your original gravity as an additional input.
How to take a reliable pre-fermentation reading
The formula is deterministic — the only variable is the quality of the Brix
reading you feed into it. These steps address the main sources of error.
Zero-calibrate before every brew session
Place a drop of distilled or reverse-osmosis water on the prism, close the cover plate, and verify the boundary line sits at 0 °Bx. If it does not, turn the calibration screw until it does. Temperature drift, handling, and previous sticky samples can shift calibration — a 0.5 °Bx error in calibration is a meaningful error in the converted SG.
Let your wort cool to room temperature first
Hot wort reads lower than its true Brix because heat lowers the refractive index. Even ATC (automatic temperature compensation) models only correct up to about 40 °C / 104 °F and are most accurate near 20 °C / 68 °F. The safest habit is to take a small sample, let it cool on the prism or in a clean vessel, and read it at room temperature.
Clean the prism between samples
Residual wort from a previous sample on the prism will blend with the new drop and shift the reading. Rinse with distilled water after each reading, then wipe gently with a lint-free cloth before the next sample. Avoid paper towels — they can scratch optical glass.
Check your model's wort correction factor (WCF)
Wort contains dextrins, proteins, and other compounds beyond simple sucrose, which shift the refractive index relative to a pure sugar solution. Some brewing-specific refractometers apply a correction factor (often labeled WCF ≈ 1.04); general-purpose refractometers do not. If your model doesn't apply a WCF, a side-by-side comparison with a calibrated hydrometer will tell you whether a systematic offset exists in your setup.
Verify with a hydrometer for high-stakes measurements
Before pitching yeast on a batch where original gravity matters — high-gravity beers, competition entries, or any recipe where efficiency tracking is important — confirm your refractometer reading with a hydrometer. The hydrometer is slower (needs a sample tube and temperature correction) but is the direct measurement instrument; the refractometer is the fast field tool. They should agree to within about ±0.001–0.002 SG on a clean unfermented sample.
Where to buy
Got your numbers? Here's where to pick up what you need:
The terms you encounter when measuring gravity, sugar content, and fermentation
progress — in plain English.
Brix (°Bx)
A scale expressing the sugar concentration of a solution as grams of sucrose per 100 grams of solution. 12 °Bx means 12 g of dissolved sugar (sucrose equivalent) per 100 g of liquid. Measured with a refractometer or a specialized Brix hydrometer. Named after Adolf Brix, who developed the scale in the 19th century.
Specific gravity (SG)
The ratio of a liquid's density to the density of pure water at the same temperature. Pure water is 1.000. A wort with SG 1.048 is 4.8% denser than water. Brewers use SG because it is what a standard hydrometer reads directly and because the difference between original and final gravity predicts alcohol content.
Gravity points
The decimal portion of specific gravity multiplied by 1,000. SG 1.048 = 48 points; SG 1.065 = 65 points. Points are used in blend calculations and are compact enough for mental arithmetic — combining equal volumes of 40-point and 80-point wort yields roughly 60-point wort.
Original gravity (OG)
The specific gravity of the wort or must before fermentation begins. OG represents the total fermentable (and unfermentable) sugar available to the yeast. Together with final gravity, OG is used to estimate alcohol content. Getting an accurate OG measurement — whether by hydrometer or by Brix-to-SG conversion — is one of the most important steps in the brew day.
Final gravity (FG)
The specific gravity measured when fermentation is complete. FG is lower than OG because yeast has consumed fermentable sugars and converted them to alcohol and CO₂, reducing the wort's density. Use a hydrometer for FG — a refractometer requires an alcohol correction that this page does not provide.
Refractometer
An optical instrument that measures the refractive index of a liquid — how sharply it bends a beam of light — and displays the result as a Brix reading. Requires only a single drop of sample; suitable for hot wort sampling (with ATC). Accurate for unfermented samples; requires an alcohol correction formula once fermentation has started.
Hydrometer
A glass float that measures liquid density directly by how deep it sinks. The scale reads specific gravity (and often Brix or potential ABV). Requires a tube of sample, is sensitive to temperature (most hydrometers are calibrated at 60 °F / 15.6 °C), and is not confused by alcohol — making it the right instrument for mid-fermentation and final gravity readings.
Automatic temperature compensation (ATC)
A feature on most modern refractometers that adjusts the refractive index reading for sample temperatures other than 20 °C / 68 °F. ATC works reliably between about 10 °C and 40 °C. It does not correct for alcohol — temperature compensation and alcohol correction are separate adjustments.
Frequently asked
Brix (°Bx) expresses sugar concentration as a percentage by weight — 12 °Bx means 12 g of dissolved sugar per 100 g of solution. Specific gravity expresses the same information as a density ratio relative to water (1.000). Both measure dissolved sugar content, just in different units, so they convert cleanly. Brewers encounter Brix on a refractometer and SG on a hydrometer — this calculator bridges the two. The only caveat is that the conversion is only accurate before fermentation adds alcohol to the liquid.
The conversion formula was built for sugar-water solutions. Once fermentation starts, alcohol is present alongside unfermented sugar. A refractometer refracts light differently in the presence of alcohol — it reads higher than the true sugar content because its optics assume the only dissolved substance is sugar. A mid-fermentation reading fed into this calculator will overstate SG. To use a refractometer during or after fermentation, you need a separate alcohol-correction formula (such as the Sean Terrill or Bonham equation) that takes your original gravity and the current refractometer reading as inputs. This calculator does not provide that correction — switch to a hydrometer for final gravity measurements.
SG = 1 + ( Brix ÷ (258.6 − ((Brix ÷ 258.2) × 227.1)) ). This is the standard three-constant polynomial used throughout the brewing and food-science industries, with constants A = 258.6, B = 258.2, and C = 227.1. It is more accurate over a wide Brix range than the simpler linear approximation (SG ≈ 1 + Brix/1000 × 4), which drifts noticeably above about 15 °Bx. Gravity points are (SG − 1) × 1000 — so SG 1.048 equals 48 points. The full derivation with a worked example at 12 °Bx is shown in the formulas section above.
Gravity points are the decimal portion of SG multiplied by 1,000 — SG 1.048 is 48 points, SG 1.065 is 65 points. Brewers use points because the numbers are compact and the arithmetic is clean: you can add and subtract points directly when blending worts, and most brewing software operates in points internally. For example, blending equal volumes of a 40-point wort and an 80-point wort yields roughly 60 points — a calculation that is awkward in SG notation (averaging 1.040 and 1.080) but trivial in points. Points appear directly in grain-bill efficiency calculations and in the standard ABV estimation formula.
For unfermented wort with no alcohol present, a properly calibrated refractometer is accurate to within roughly ±0.001 SG of a hydrometer reading. The main error sources are temperature (calibrate and read at room temperature, ideally 20 °C / 68 °F), calibration drift (zero-calibrate with distilled water before each session), contamination from a previous sample on the prism, and the wort correction factor — some brewing refractometers apply a WCF of approximately 1.04 to account for non-sugar dissolved solids in wort; general-purpose refractometers do not. Once fermentation has started, accuracy degrades substantially due to the alcohol effect described above — switch to a hydrometer for all post-pitching readings.
For beer, most homebrew recipes fall between 8 and 20 °Bx at the start of fermentation — roughly SG 1.032 to SG 1.082. Session beers sit at the low end (8–11 °Bx); standard ales and lagers are commonly 10–14 °Bx; high-gravity beers and barleywines can reach 20–28 °Bx. For wine, fresh grape juice typically measures 18–26 °Bx, with late-harvest styles sometimes exceeding 30 °Bx. Cider falls between beer and wine, usually 11–18 °Bx depending on the apple variety and any added sugar. The formula on this page is reliable up to about 40 °Bx, covering all of these ranges.
The Brix scale is used widely in food and beverage quality control beyond brewing — including coffee, juice, soft drinks, and syrup production. For cold-brew coffee, a refractometer reading in Brix gives a useful consistency benchmark from batch to batch. However, the Brix-to-SG conversion applies most accurately to solutions where sucrose is the primary dissolved solid. Cold-brew coffee contains acids, oils, caffeine, and other compounds that contribute to the refractometer reading without being sugar — so the resulting SG is an approximation rather than a precise density measurement. It is useful for relative comparisons, not literal density claims.
Original gravity (OG) is the specific gravity of your wort or must before fermentation begins. It tells you how much fermentable sugar the yeast has to work with. Final gravity (FG) is measured after fermentation is complete. The difference is proportional to alcohol produced: ABV ≈ (OG − FG) × 131.25. For example, OG 1.052 and FG 1.010 gives about 5.5% ABV. An accurate OG reading — whether via hydrometer or by converting a Brix reading using this calculator — is one of the most important measurements in homebrewing. Brew responsibly, and be aware of your finished product's actual alcohol content.
Common mistakes with the Brix to gravity calculator
A refractometer is one of the most useful tools in a brewer's kit — and one of the most misused. These mistakes account for most of the confusion.
Using this calculator on fermented beer
This is the most important limitation: this calculator converts Brix to specific gravity for unfermented wort only. Once alcohol is present, it distorts the refractometer reading upward — your refractometer will show a Brix value that is higher than the true sugar content, and the resulting SG will be higher than the actual gravity of the beer. For any mid-fermentation or post-fermentation measurement, use a hydrometer or apply the Novotný alcohol correction formula. The footer disclaimer on this page says the same thing.
Not zero-calibrating with distilled water before each session
A clean refractometer reading distilled water should show exactly 0.0 °Bx. If it doesn't, use the calibration screw to set it to zero. A 0.5 °Bx calibration error translates to roughly 0.002 SG and about 0.25% ABV in your final calculation — small, but compounding. Calibrate at the start of every brew session, not once a month.
Reading very hot wort and trusting ATC to compensate fully
Automatic temperature compensation (ATC) is built into most refractometers, but ATC models are only accurate close to their rated temperature range (typically 10–30 °C / 50–86 °F). Taking a sample directly from a 90 °C kettle and reading it immediately exceeds that range, even if the optics cool slightly. Take a small sample, set it aside for 30–60 seconds to approach ambient temperature, then read it.
Ignoring your instrument's wort correction factor
Some refractometers — particularly those marketed for brewing — apply a wort correction factor (WCF, typically around 1.04) to adjust for the fact that wort scatters light slightly differently than a pure sucrose solution. If your instrument applies a WCF, it will be noted in the manual. Check one reading against a hydrometer on an unfermented sample to confirm they agree; if they don't, your instrument may need a WCF adjustment.