Homebrew ABV Calculator
Work out alcohol by volume from your original and final gravity, plus attenuation, ABW and calories.
Enter your original and final gravity — everything updates as you type.
Alcohol by volume
Gravities used: OG 1.0500 · FG 1.0100
- ABV — standard formula
- —
- ABV — alternate (Hall)
- —
- Alcohol by weight (ABW)
- —
- Apparent attenuation
- —
- Real attenuation
- —
- Gravity in °Plato
- —
- Gravity points dropped
- —
- Calories per 12 oz (355 ml)
- —
- Calories per 330 ml
- —
- US standard drinks per 12 oz
- —
How it works
Alcohol by volume comes from the sugar your yeast ate — the drop between your
original gravity (before pitching) and your final gravity
(when fermentation is done). This calculator shows two accepted formulas side by side. The
standard one is the homebrew rule of thumb
ABV% = (OG − FG) × 131.25. The alternate one is Hall's formula from
Brew by the Numbers:
ABV% = (76.08 × (OG − FG) ÷ (1.775 − OG)) × (FG ÷ 0.794), which stays accurate on
big beers, wines and meads where the simple multiplier drifts high. For OG 1.050 → FG 1.010
they give 5.25% and 5.34%.
From the same two numbers it also derives apparent attenuation
(OG − FG) ÷ (OG − 1), real attenuation via real extract
RE = 0.1808 × OG°P + 0.8192 × FG°P, alcohol by weight
ABW = ABV × 0.789 ÷ FG, degrees Plato from the standard cubic
°P = −616.868 + 1111.14·SG − 630.272·SG² + 135.997·SG³, and calories using the
familiar alcohol + carbohydrate pair
1881.22 × FG × (OG − FG) ÷ (1.775 − OG) and
3550 × FG × (0.1808·OG + 0.8192·FG − 1.0004).
You can type readings as specific gravity or as °Plato/°Brix (converted with
SG = 1 + P ÷ (258.6 − (P ÷ 258.2) × 227.1)). Tick the temperature box if you read
a warm sample: the calculator applies the usual hydrometer correction curve for the difference
between your sample temperature and your hydrometer's calibration temperature. One caveat —
a refractometer reading taken after fermentation starts is skewed by alcohol
and needs a separate refractometer correction before you use it here. Everything runs in your
browser in plain JavaScript: no uploads, no sign-up, no ads.
These are estimates: real ABV depends on how accurately you took your readings, on yeast health and on unfermentable sugars. Calorie figures assume a finished, fully fermented beverage and are not nutrition advice. Please drink responsibly.
Frequently asked questions
How do you calculate ABV from OG and FG?
The homebrew standard is ABV% = (OG − FG) × 131.25, so an OG of 1.050 finishing at 1.010 gives 5.25%. For stronger worts this calculator also shows Hall's alternate formula, ABV% = (76.08 × (OG − FG) ÷ (1.775 − OG)) × (FG ÷ 0.794), which gives 5.34% for the same beer and stays accurate above 1.070.
What is the difference between apparent and real attenuation?
Apparent attenuation is (OG − FG) ÷ (OG − 1) and reads high because alcohol is lighter than water, so the hydrometer under-reports the sugar that is left. Real attenuation corrects for that using real extract, RE = 0.1808 × OG°P + 0.8192 × FG°P. A beer at 80.0% apparent attenuation is about 65.0% real.
Can I use a refractometer reading in this calculator?
Use it for the original gravity only. Once fermentation starts, alcohol bends light and skews a refractometer, so a post-fermentation Brix reading needs a refractometer correction first — or just take the final gravity with a hydrometer. You can enter readings as specific gravity or °Plato/°Brix, and tick the temperature box to correct a warm hydrometer sample.