Potential Alcohol Calculator (Wine, Cider, Mead, Beer)
Potential ABV from the starting gravity, Brix or Baumé of a must, juice or wort — fermented dry or to a chosen final gravity — by the standard, alternative, Hall, Balling and winemaker formulas, with hydrometer temperature correction, refractometer final readings, sugar added later, attenuation, calories and an ABV-by-final-gravity table.
How it works
Standard: ABV = (OG − FG) × 131.25. Alternative (Hall): ABV = 76.08 × (OG − FG) ÷ (1.775 − OG) × (FG ÷ 0.794). Hall polynomial: ABV = (OG − FG) × (100.3 × (OG − FG) + 125.65). Balling: RE = (q·OE + AE) ÷ (1 + q), q = 0.22 + 0.001·OE; ABW = (OE − RE) ÷ (2.0665 − 0.010665·OE); ABV = ABW × FG ÷ 0.794. Winemaker: ABV = gravity points dropped ÷ 7.36
Yeast turns roughly half the weight of sugar into ethanol and half into carbon dioxide that bubbles away, so the drop in density between the starting and finished liquid tracks the alcohol made. The familiar factor of 131.25 works well at beer strengths but reads low for strong wines and meads. There the alternative formula, which allows for the changing density of the alcohol-water mix, can differ by almost a full percentage point at 1.100. The Balling method used by brewing labs works from the real extract and lands close to it. Winemakers often divide the gravity points by 7.36 or use the Brix shortcut of 0.55–0.6% alcohol per degree. The calculator shows every method side by side and lets you choose which one drives the main result. Under More options it corrects hydrometer readings for sample temperature, turns a refractometer final reading into a true final gravity (the Terrill correction), and adds sugar fed after the starting reading. The final gravity matters: a wine yeast will take a must to 0.992, while a beer yeast leaves unfermentable dextrins around 1.010. The table shows the alcohol for each possible finishing point.
Worked example
A must at 1.092 (22 °Bx) fermented dry to 0.994 drops 98 gravity points. The standard formula gives 0.098 × 131.25 = 12.9%. The alternative formula gives 76.08 × 0.098 ÷ 0.683 × 1.252 = 13.7%, Balling 13.0%, Hall’s polynomial 13.3% and the winemaker’s ÷ 7.36 rule 13.3%: a strong dry wine. Feeding 1 kg of table sugar into 20 L later adds about 19 gravity points and roughly 2.5% more alcohol.
Sources: Brewer’s Friend — ABV equations (standard and alternate) · Sean Terrill — refractometer FG results (cubic correction)
Frequently asked questions
Which formula should I trust?
Below about 1.070 they agree within 0.2%. Above that, prefer the alternative or Balling result. Competition organisers generally accept any of them, but say which one you used. You can pick the formula that drives the main result, and the others stay listed for comparison.
How much sugar raises potential alcohol by 1%?
About 17–18 g of sugar per litre (2.3 oz per US gallon) for wine. Enter a later addition under More options to see its effect, or use the chaptalization calculator to plan one.
Can I use a refractometer for the final reading?
Yes, with a correction. Alcohol bends light differently from sugar, so the raw °Brix after fermentation reads high. Turn on the refractometer option and the Terrill cubic converts it to a true final gravity. It was fitted to beer wort, so confirm wine and mead readings with a hydrometer.
Does sample temperature matter?
Yes. A hydrometer calibrated at 20 °C (68 °F) reads low in warm must: 1.090 at 30 °C is really about 1.093. Turn on the temperature correction and enter the sample and calibration temperatures.
What is the difference between alcohol by volume and by weight?
ABV is what appears on labels. Alcohol by weight is lower because ethanol is lighter than water: 12.9% by volume is about 10.2% by weight in a dry wine.
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This calculator is for educational purposes. Double-check important results before acting on them.