Enter your batch volume, original gravity (OG) and final gravity (FG) to calculate ABV, apparent attenuation and estimated calories per 250 ml glass of your home brew.
Enter your batch volume in litres. Then input the original gravity (OG) measured with a hydrometer or refractometer before fermentation starts. After fermentation is complete, enter the final gravity (FG). The calculator will show ABV, attenuation and approximate calories.
Batch size 20 litres. OG = 1.050, FG = 1.010. ABV = (1.050 – 1.010) × 131.25 = 5.3%. Attenuation = (1.050 – 1.010) / (1.050 – 1.0) × 100% = 80%. Calories per 250 ml glass ≈ 122 kcal.
OG is the density of the wort before fermentation, measured in SG units. It indicates the amount of fermentable sugars and helps predict the final alcohol content of the beer.
FG is the density of the beer after fermentation is complete. A lower FG means more sugars were fermented by yeast, resulting in higher alcohol content in the finished beer.
ABV = (OG - FG) × 131.25. This simplified formula is widely used by homebrewers and gives results accurate to within ±0.3% for most standard beers.
Attenuation is the percentage of sugars converted by yeast into alcohol and CO2. It is calculated as: (OG - FG) / (OG - 1.0) × 100%. Typical values range from 70% to 85%.
The calculator estimates calories in a 250 ml glass. A typical 5% lager contains around 100-130 kcal per glass. Stronger beers have proportionally more calories.
Gravity is measured with a hydrometer or refractometer. A hydrometer is submerged directly in the wort; a refractometer only needs a few drops and is more convenient during the brewing process.
Light beers: OG 1.028-1.040, lagers: 1.040-1.055, ales: 1.045-1.060, IPAs: 1.055-1.075, strong beers: 1.075-1.120. Higher OG means sweeter wort and greater alcohol potential.
Attenuation is influenced by yeast strain and health, fermentation temperature, mash composition (ratio of fermentable to non-fermentable sugars) and fermentation duration.
Fermentation is complete when gravity stabilises at the same reading for 2-3 consecutive days. Never bottle beer without confirming a stable FG — unstable beer can cause bottle bombs.
Yes, the ABV formula is universal for fermented beverages. For home cider or wine, simply enter the gravity before and after fermentation in the same way.
Results are indicative only and do not constitute brewing or medical advice. Accuracy depends on gravity measurement precision. ABV may differ from actual by ±0.3%.
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