About the ABV Calculator
This ABV calculator works out the alcohol by volume of homebrewed beer, wine, cider, mead or kombucha from two hydrometer readings: the original gravity (OG) taken before fermentation and the final gravity (FG) taken when fermentation has finished. Yeast turns sugar into alcohol and carbon dioxide, and because alcohol is lighter than water the gravity drops — the size of that drop tells you how much alcohol was made.
It offers the standard homebrewing formula, ABV = (OG − FG) × 131.25, which is accurate for most beers, and an alternate formula that corrects for the non-linear behaviour of high-gravity worts such as barleywines, imperial stouts and strong meads. Alongside ABV you get alcohol by weight, apparent attenuation (how much of the sugar the yeast consumed), both gravities in degrees Plato and an estimate of calories per 12 oz serving.
Readings should be temperature-corrected to your hydrometer’s calibration temperature (usually 60°F or 68°F). If you use a refractometer, remember that alcohol distorts its final reading, so convert the FG with a refractometer correction before using this tool.
With the default inputs, the alcohol by volume (abv) is 5.25%. Change any value above to recalculate instantly.
How to use the abv calculator
- 1Take a hydrometer reading of the wort or must before pitching yeast (OG).
- 2Take the final reading once gravity is stable for several days (FG).
- 3Enter both readings, corrected for temperature.
- 4Choose the alternate formula for strong beers, wines and meads.
- 5Read ABV, attenuation and calories to log your batch.
Formula and method
The standard formula multiplies the drop in specific gravity by 131.25, a constant derived from how much ethanol a given amount of fermented sugar produces and ethanol’s density. It is accurate to within a few tenths of a percent for beers up to about 7% ABV. The alternate formula adjusts for the fact that the relationship becomes non-linear in stronger worts, so it gives slightly higher, more realistic figures above about 1.070 OG.
Alcohol by weight is ABV × 0.789 (the density of ethanol) ÷ FG. Apparent attenuation is the gravity drop as a share of the original gravity points. Degrees Plato use the ASBC polynomial, and calories use the standard real-extract method for a 12 oz serving.
- OG
- Original specific gravity before fermentation
- FG
- Final specific gravity after fermentation
- °P
- Degrees Plato — percent sugar by weight
Worked examples
Pale ale: OG 1.050, FG 1.010
A 40-point gravity drop × 131.25 gives 5.25% ABV. The yeast consumed 40 of 50 gravity points, an 80% apparent attenuation. The wort started at about 12.4°Plato and a 12 oz bottle has roughly 164 calories.
Imperial stout: OG 1.100, FG 1.025 (alternate)
With 75 points of gravity drop the standard formula gives 9.84%, but the alternate high-gravity formula gives about 10.9% ABV, which better reflects strong beers. Attenuation is 75%.
Dry cider: OG 1.055, FG 0.998
Cider ferments almost completely, finishing below 1.000 because alcohol is lighter than water. A 57-point drop gives about 7.5% ABV and an apparent attenuation above 100%.
Frequently asked questions
How do you calculate ABV from gravity?+
Subtract the final gravity from the original gravity and multiply by 131.25. For example (1.050 − 1.010) × 131.25 = 5.25% ABV. For strong worts above 1.070, the alternate formula is more accurate.
What is a normal final gravity for beer?+
Most ales finish between 1.008 and 1.016 and lagers between 1.006 and 1.012. Big, malty beers may finish at 1.020–1.030, while dry wines and ciders often end below 1.000.
Can apparent attenuation be over 100%?+
Yes. Apparent attenuation compares hydrometer readings, and alcohol is less dense than water, so a fully fermented cider or wine can read below 1.000 and show more than 100% apparent attenuation.
Do I need to correct hydrometer readings for temperature?+
Yes. Hydrometers are calibrated at a set temperature, usually 60°F (15.6°C) or 68°F (20°C). Warm samples read low; correct them or cool the sample before measuring so your ABV is accurate.
What is the difference between ABV and ABW?+
ABV is the volume of alcohol as a share of the drink’s volume; ABW is its share by weight. Because ethanol is lighter than water, ABW is about 80% of ABV — a 5% ABV beer is about 4% ABW.