ABV Calculator (Alcohol by Volume)

Final Gravity (FG) measures the density of your beer after fermentation is complete. A lower FG indicates more sugar has been converted to alcohol. Measure FG when airlock activity has stopped for 48–72 hours, then take two readings 24 hours apart. If both readings are identical, fermentation is complete. Typical FGs range from 1.006 to 1.018 for most beer styles.

The standard formula (×131.25) is accurate for most homebrewed beers below 7–8% ABV. At higher gravity levels, the relationship between gravity drop and alcohol yield becomes non-linear due to changes in solution density at high ethanol concentrations. The alternate formula (÷0.00753) and the more complex Brix/refractometer formula provide better accuracy for strong beers, wines, and high-gravity meads. The difference between methods is typically 0.1–0.3% ABV for normal beers.

Refractometers become inaccurate once alcohol is present because ethanol refracts light differently than sugar water. To use a refractometer post-fermentation, apply a Brix correction formula: FG = 1.001843 − 0.002318474 × Brix_OG − 0.000007775 × Brix_OG² − 0.000000034 × Brix_OG³ + 0.00574 × Brix_FG + 0.00003344 × Brix_FG² + 0.000000086 × Brix_FG³. A standard hydrometer does not require correction after fermentation.

Apparent attenuation (calculated from gravity readings) is slightly higher than real attenuation because ethanol is less dense than water, causing the final gravity reading to appear lower than the true dissolved solids content. Apparent attenuation typically runs 3–4% higher than real attenuation. For practical homebrewing purposes, apparent attenuation is sufficient for comparing yeast strains and monitoring fermentation progress.

The calorie estimate is approximate. Alcohol contributes ~7 kcal/gram (55 kcal per 8g in a 12 oz standard beer). Residual sugars contribute ~4 kcal/gram. The estimate in this calculator uses ABV as the primary driver and applies an empirical multiplier. Actual calories can vary by 10–15% based on exact sugar composition, protein content from malts, and serving temperature (carbonation loss). For certified nutritional data, laboratory analysis is required.

Low ABV despite normal gravity readings can result from: (1) inaccurate OG measurement (wort not fully mixed before sampling); (2) incomplete fermentation due to insufficient yeast pitch rate; (3) low fermentation temperature inhibiting yeast activity; (4) nutrient deficiency (especially in high-adjunct beers); (5) wild yeast or bacterial contamination that produces non-alcoholic fermentation byproducts. If FG appears too high, warm the fermentor to 68–72°F and gently rouse the yeast.

Yes. Wine makers use the same gravity-based formulas. A dry red wine typically starts at OG 1.090–1.100 (equivalent to ~21–23 Brix) and finishes at FG 0.990–1.000. The alternate method or Brix method is recommended for wine due to its higher alcohol content compared to typical beer. Note that refractometer readings on wine are especially unreliable post-fermentation due to high ethanol levels.

Hydrometer readings must be temperature-corrected. Most hydrometers are calibrated to 60°F (15.6°C). Wort or beer at higher temperatures appears less dense due to thermal expansion. Apply a correction factor: add approximately 0.001 SG per 7°F (4°C) above calibration temperature. Many brewing calculators include a built-in temperature correction. Refractometers should be zeroed with distilled water at room temperature before each session.

In the United States, beverages with 0.5% ABV or more are classified as alcoholic by federal law (TTB regulations). Commercial labels must show ABV within a legal tolerance: ±0.3% for beers under 7% ABV, ±0.5% for higher-strength beers. In the EU, the ABV must be stated to one decimal place with a tolerance of ±0.5%. Homebrewed beverages are exempt from labeling requirements in most jurisdictions but are subject to production volume limits.