ABV Calculator

How to use

1. 1Choose your reading unit: specific gravity (SG, where water is 1.000) or degrees Brix from a refractometer.
2. 2Pick a formula: Standard for ordinary-strength drinks, or Alternate for strong beers and wines above about 6 to 7 percent.
3. 3Enter the original gravity (the reading before fermentation) and the final gravity (the reading after).
4. 4Read the alcohol by volume, plus both formula results, apparent attenuation, and an estimated calorie count per serving.
5. 5Optionally enter a batch volume and target ABV in the dilution helper to see how much water to add.
6. 6Use Copy summary to save the results, load a worked example to start from, or Reset to return to the defaults.

About this tool

ABV Calculator works out the alcohol by volume of a fermented drink from two hydrometer or refractometer readings: the original gravity (OG) taken before fermentation and the final gravity (FG) taken after. Fermentation converts sugar into alcohol and carbon dioxide, so the liquid becomes lighter, and the size of that drop is what the alcohol content is read from. This is the single most common calculation in homebrewing, winemaking, cider, mead, and kombucha, and this tool does it in your browser with no signup. Two industry-standard equations are built in, both expressed in specific gravity where pure water reads 1.000. The standard formula is ABV = (OG - FG) x 131.25, where the 131.25 constant folds together the density of ethanol (about 0.79) and the ratio of ethanol produced per unit of sugar fermented; it is the formula taught in nearly every beginner brewing book and is accurate for ordinary-strength drinks, roughly under 6 to 7 percent. The alternate formula, derived by Cutaia, Reid and Speers in 2009, is ABV = (76.08 x (OG - FG) / (1.775 - OG)) x (FG / 0.794); it corrects for high-gravity beers and wines, where the large amount of alcohol changes the density in a non-linear way and the standard formula begins to read low. The two agree closely at low strength and diverge as the starting gravity climbs, so the calculator always shows both and lets you pick which one drives the headline figure. Readings can be entered as specific gravity (1.050) or in degrees Brix, the refractometer scale common in winemaking; Brix is converted to specific gravity with the standard refractometer polynomial before the ABV math runs, and the equivalent SG is shown for reference. Alongside the ABV the tool reports apparent attenuation, the share of the starting sugar that fermented out, which is a quick check on how complete the fermentation was, and an estimated calorie count per 12 fl oz (355 ml) serving from both alcohol and residual carbohydrates. An optional dilution helper takes the batch volume and a target strength and tells you how much water to add, since adding water lowers the ABV in proportion to the new total volume. Worked-example presets load a pale ale, an imperial stout, a dry wine, a cider, and a kombucha so you can see realistic numbers and then edit them. A few honest limits: take both readings at the temperature your hydrometer is calibrated for or apply a temperature correction first; a refractometer over-reads at the end of fermentation because alcohol bends light differently from sugar, so a calibrated hydrometer FG is more dependable for the final number; and the calorie figure is an estimate, not a lab measurement. Every value is plain arithmetic computed on your device, so the readings you enter are never uploaded, logged, or stored.

Free to use. Works in your browser. No signup, no login.