What is my brew’s ABV?
Enter your hydrometer readings before and after fermentation. See the alcohol by volume, by the standard formula or the alternate one for strong brews.
- Alcohol by volume
- 5.25%
From 1.05 down to 1.01, the ABV is 5.25%.
- Alcohol by weight
- 4.13%
- Apparent attenuation
- 80%
Alcohol by volume: 5.25%. From 1.05 down to 1.01, the ABV is 5.25%.
How to calculate
Computes the alcohol by volume of beer, wine, cider or mead from the original and final specific gravity, by the standard formula or the alternate formula for strong brews, with alcohol by weight and apparent attenuation.
Example with the default inputs (Original gravity (OG) 1.05, Final gravity (FG) 1.01, Formula Standard): From 1.05 down to 1.01, the ABV is 5.25%.
Method: standard: ABV = (OG − FG) × 131.25; alternate: ABV = 76.08 × (OG − FG) ÷ (1.775 − OG) × FG ÷ 0.794; ABW = ABV × 0.794 ÷ FG
- Gravities are specific gravities measured at the hydrometer’s calibration temperature, or corrected to it.
- Apparent attenuation uses the measured final gravity, which alcohol lowers, so it can pass 100% in a dry wine or cider.
- Sugar added after the original reading (priming or feeding) is not counted.
Worked examples
Each example is checked against the calculator on every build.
- Original gravity (OG) 1.05, Final gravity (FG) 1.01, Formula Standard gives Alcohol by volume 5.25%, Apparent attenuation 80%.Source: hand calculation in content.mdx: (1.050 − 1.010) × 131.25 = 5.25%; 0.040 ÷ 0.050 = 80%
- Original gravity (OG) 1.05, Final gravity (FG) 1.01, Formula Alternate gives Alcohol by volume 5.339411%, Alcohol by weight 4.197517%.Source: Hall, Brew by the Numbers, Zymurgy 18(2), 1995, as cited in content.mdx; hand calculation in content.mdx: 76.08 × 0.040 ÷ 0.725 = 4.198% ABW; × 1.010 ÷ 0.794 = 5.34% ABV
- Original gravity (OG) 1.1, Final gravity (FG) 1.02, Formula Alternate gives Alcohol by volume 11.583409%.Source: hand calculation in content.mdx: 76.08 × 0.080 ÷ 0.675 = 9.017; × 1.020 ÷ 0.794 = 11.58% (standard: 10.50%)
- Original gravity (OG) 1.09, Final gravity (FG) 0.995, Formula Standard gives Alcohol by volume 12.46875%, Apparent attenuation 105.555556%.Source: hand calculation in content.mdx: 0.095 × 131.25 = 12.47%; 0.095 ÷ 0.090 = 105.6%
How it works
OG is the original gravity, before fermentation; FG is the final gravity, after it. Both are specific gravities, such as 1.050.
- Standard formula: ABV = (OG − FG) × 131.25.
- Alternate formula (Hall, 1995): ABW = 76.08 × (OG − FG) ÷ (1.775 − OG), and ABV = ABW × FG ÷ 0.794, where 0.794 is the specific gravity of ethanol.
- Alcohol by weight, for either formula: ABW = ABV × 0.794 ÷ FG.
- Apparent attenuation = (OG − FG) ÷ (OG − 1) × 100%.
The final gravity may not be above the original gravity. OG runs from 1.001 to 1.200 and FG from 0.980 to 1.200.
Worked examples by hand
A pale ale, 1.050 to 1.010, standard formula. 1.050 − 1.010 = 0.040. 0.040 × 131.25 = 5.25% ABV. Attenuation 0.040 ÷ 0.050 = 80%.
The same beer, alternate formula. 76.08 × 0.040 ÷ (1.775 − 1.050) = 3.0432 ÷ 0.725 = 4.198% ABW. ABV = 4.198 × 1.010 ÷ 0.794 = 5.34%.
A barleywine, 1.100 to 1.020, alternate formula. 76.08 × 0.080 ÷ 0.675 = 9.017% ABW; × 1.020 ÷ 0.794 = 11.58% ABV. The standard formula gives 0.080 × 131.25 = 10.50%.
A dry wine, 1.090 to 0.995, standard formula. 0.095 × 131.25 = 12.47% ABV. Attenuation 0.095 ÷ 0.090 = 105.6%.
Other questions people ask
How do I calculate ABV from gravity?
Subtract the final gravity from the original gravity and multiply by 131.25. A beer that goes from 1.050 to 1.010 is 0.040 × 131.25 = 5.25% ABV.
When should I use the alternate formula?
The standard formula is a straight line and reads low for strong brews. The alternate formula, from Michael Hall’s 1995 Zymurgy article, allows for the original gravity. For 1.100 down to 1.020 it gives 11.58% against the standard 10.50%. For normal beers the two are close.
What is the difference between ABV and ABW?
ABV is the alcohol as a share of the volume; ABW is its share of the weight. Alcohol is lighter than water, so ABW is lower: ABW = ABV × 0.794 ÷ FG. A 5% ABV beer at FG 1.010 is about 3.9% ABW.
What is apparent attenuation?
The share of the gravity above water that fermented away: (OG − FG) ÷ (OG − 1). It is apparent because alcohol is lighter than water, so the hydrometer reads lower than the sugar left; a dry wine can show more than 100%.
Do I need to correct my hydrometer reading for temperature?
Yes, if the sample is not at the temperature the hydrometer is calibrated for (printed on it or in its instructions). Correct both readings first, then enter them here.
What if I added sugar during fermentation?
The formula only sees the gravity change it is given. Sugar added after the original reading adds alcohol the readings do not show, so the result reads low.