Homebrew ABV Calculator

How ABV Is Calculated for Homebrew

Alcohol by Volume (ABV) measures the percentage of alcohol in your finished beer. It’s calculated from the difference between your Original Gravity (OG) and Final Gravity (FG).

Standard ABV Formula: ABV = (OG − FG) × 131.25

This formula is accurate for beers under ~10% ABV.

More Accurate Formula (for high-gravity beers): ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)

Gravity Notation: Specific gravity is measured with a hydrometer or refractometer. Water = 1.000. A beer OG of 1.050 has 50 “gravity points” above water.

Worked Example: American Pale Ale: OG = 1.052, FG = 1.010

• ABV = (1.052 − 1.010) × 131.25 = 0.042 × 131.25 = 5.5% ABV

ABV Reference by Style:

• Light lager: 3.5–4.5%
• American Pale Ale: 4.5–6.0%
• IPA: 5.5–7.5%
• Double IPA: 7.5–10%
• Belgian Tripel: 7.5–9.5%
• Russian Imperial Stout: 8–13%
• Barleywine: 10–15%

Attenuation: Apparent Attenuation = ((OG − FG) / (OG − 1.000)) × 100 Most ale yeasts attenuate 70–80%. Example: (1.052 − 1.010) / (1.052 − 1.000) × 100 = 42/52 × 100 = 80.8% attenuation

Higher attenuation = drier, less sweet beer.

Hydrometer vs Refractometer: A hydrometer measures gravity directly in liquid wort — use it for final gravity. A refractometer works on a single drop and is great for checking OG, but requires a correction formula for post-fermentation readings because alcohol changes the refractive index. Always verify your FG with a hydrometer before calculating final ABV.