This ABV calculator works out the alcohol by volume of a beer, wine, cider, mead or spirit wash from two hydrometer readings. Take your original gravity (OG) before fermentation and your final gravity (FG) once it has finished. The standard home brewing formula is ABV = (OG − FG) × 131.25. For strong washes and wines, the more accurate formula (tick the box) gives a slightly higher figure.
Worked example
A beer starts at 1.050 and finishes at 1.010. (1.050 − 1.010) × 131.25 = 5.25%, so the beer is about 5.3% ABV. A sugar wash that goes from 1.090 down to 0.990 is about 13.1% ABV with the standard formula, or about 13.9% with the more accurate one.
How to take an accurate reading
- Fill a test jar with a sample, float the hydrometer and spin it to knock off bubbles.
- Read where the liquid surface crosses the scale, at eye level.
- Take readings near 20°C, or correct for temperature. Warm samples read low.
- Confirm fermentation has finished with the same reading two or three days apart.
FAQ
Why are there two formulas?
(OG − FG) × 131.25 is quick and accurate enough for most beers. Above about 8% ABV it under-reads, so the second formula is better for wines and strong washes.
What is attenuation?
The share of the sugar the yeast has fermented, based on your readings. Most beer yeasts reach 70–80%; turbo yeast washes usually go well below 1.000.
Can I use this for a spirit after distilling?
No. Once a liquid is distilled, a hydrometer can't read its alcohol. Use an alcometer on the spirit instead.
My wash reads below 1.000. Is that right?
Yes. Alcohol is lighter than water, so a fully fermented wash often finishes around 0.990 to 0.995.
Gear and guides: hydrometers and testing gear, wash hydrometer, how to brew beer at home, distiller's sugar wash recipe. More tools: spirit dilution calculator, priming sugar calculator, essence calculator.
