Alcohol Content (ABV) & Units Calculator

Homebrewing ABV Guide

The ABV Formula

ABV (%) ≈ (OG − FG) × 131.25, where OG and FG are specific gravity readings. The simplified Milligan formula: ABV = (OG − FG) × 131.25 is accurate for most beers and wines (under 15% ABV). For high-gravity beers and wines, the more precise formula is: ABV = ((1.05 × (OG − FG)) / FG) / 0.79 × 100. Example: OG 1.060, FG 1.010 → ABV = (0.050) × 131.25 = 6.56%. This formula accounts for the fact that yeast converts sugars to alcohol and CO₂ rather than directly measuring alcohol.

Using a Hydrometer

A hydrometer measures the density of liquid relative to water (specific gravity). Water = 1.000. Adding sugar increases density above 1.000 (typical wort: 1.040–1.080). As yeast ferments sugars into alcohol, density decreases toward 1.000 or below. Take readings at the same temperature (usually calibrated for 20°C — apply temperature correction otherwise). Hydrometer readings are affected by bubbles — degas the sample by shaking or warming slightly before measuring final gravity.

Typical Gravity and ABV Targets

Session beer (3–4% ABV): OG 1.030–1.040. Standard ale (4–5% ABV): OG 1.040–1.050. Strong ale (5–7% ABV): OG 1.050–1.070. Strong beer / barleywine (8–12% ABV): OG 1.080–1.110. Table wine (10–13% ABV): OG 1.075–1.095. High-gravity wine (14–17% ABV): OG 1.100–1.130. The yeast strain determines maximum attenuation — wine yeast (up to 18% ABV) can ferment much further than typical beer yeast (8–10% ABV).

Is Fermentation Complete?

Fermentation is complete when: gravity readings taken 2 days apart are identical, and the reading matches the expected FG for the recipe/yeast. Do not bottle based on time alone — bottling too early traps residual CO₂ production, causing bottles to over-pressurise (bottle bombs). Common FG ranges: most ale yeast 1.008–1.015, wine yeast 0.990–1.005, Belgian/saison yeast 1.004–1.008. A stuck fermentation (gravity stops moving above expected FG) may indicate temperature problems, nutrient deficienc