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🍺 ABV Calculator

Enter your original and final gravity to get the ABV, with the more accurate high-gravity formula, attenuation and calories too.

ABV (standard)

5.25%

ABV (accurate)

5.34%

Attenuation

80%

Calories / 12 oz

165

The standard estimate is ABV = (OG − FG) × 131.25. The "accurate" figure uses Michael Hall's formula, which is better for strong beers (above ~1.070) where the simple one reads a little low. Attenuation is how much of the sugar fermented; calories are a standard estimate per 12 oz (355 mL) serving. Gravities are specific gravity (water = 1.000). 🔒 In your browser.
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How the abv calculator works

As yeast ferments sugar into alcohol and CO₂, the wort gets less dense, so the drop in gravity tells you how much alcohol was made. The standard estimate is ABV = (OG − FG) × 131.25. The tool also shows Michael Hall's more accurate formula (better for strong beers), the apparent attenuation (how much sugar fermented) and an estimate of the calories per serving.

The simple ×131.25 formula is spot-on for typical beers but reads slightly low above about 1.070, use the "accurate" figure for big beers. Gravities are specific gravity (water = 1.000); if you measured with a refractometer after fermentation started, correct the final reading first (alcohol skews refractometers), which the refractometer tool handles.

Frequently asked questions

How do I calculate ABV from OG and FG?

ABV = (original gravity − final gravity) × 131.25. For OG 1.050 and FG 1.010 that's (0.040) × 131.25 ≈ 5.25% ABV. For strong beers above ~1.070, use the more accurate formula the tool also shows.

What is the difference between the two ABV formulas?

The simple one (×131.25) is a linear approximation that's accurate for normal-strength beers. Michael Hall's formula accounts for the non-linear relationship at higher gravities, where the simple version underestimates by more than 0.2% ABV.

What is attenuation?

The percentage of the original sugar the yeast fermented: (OG − FG) ÷ (OG − 1). Typical ales finish around 70-80%. Low attenuation means a sweeter, fuller beer; high attenuation a drier one.

How are the calories calculated?

From the alcohol and residual carbohydrates using the original and final gravity, per 12 oz (355 mL) serving. It's a standard homebrew estimate, most of the calories come from the alcohol, with the rest from unfermented sugars.

Why is my ABV different from the label of a similar beer?

ABV depends on your exact OG and FG, which vary with your recipe, yeast and fermentation. Two beers of the same style can differ by a percent or more. The calculation is only as good as your gravity readings, take them at the right temperature.

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