ABV Calculator for Homebrewers
Calculate the alcohol content of your homebrew from gravity readings. Enter your Original Gravity and Final Gravity below.
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How the ABV Formula Works
When you brew beer, you start with a sugary liquid called wort. A hydrometer measures the density of this liquid compared to water. Pure water reads 1.000. Wort with dissolved sugars reads higher — typically between 1.030 and 1.100.
This pre-fermentation reading is your Original Gravity (OG).
Yeast eats the sugars and produces alcohol and CO2. Alcohol is lighter than water, so the density drops. After fermentation finishes, you take another reading — your Final Gravity (FG).
The difference between these two numbers tells you how much sugar was converted to alcohol. The standard formula is:
ABV = (OG - FG) x 131.25The alternate formula (sometimes called the Daniels/Hall method) is slightly more accurate for higher-gravity beers:
ABV = (76.08 x (OG - FG) / (1.775 - OG)) x (FG / 0.794)For most homebrews, both formulas give very similar results. The difference becomes noticeable above 8% ABV.
Frequently Asked Questions
How do I calculate ABV from gravity readings?
Subtract your Final Gravity (FG) from your Original Gravity (OG) and multiply by 131.25. For example, an OG of 1.050 and FG of 1.010 gives (1.050 - 1.010) x 131.25 = 5.25% ABV.
What is the difference between OG and FG?
Original Gravity (OG) is the density of your wort before fermentation, measuring dissolved sugars. Final Gravity (FG) is the density after fermentation is complete. The difference tells you how much sugar the yeast converted to alcohol.
What is apparent attenuation?
Apparent attenuation measures what percentage of sugars the yeast appeared to consume, calculated from hydrometer readings. It typically ranges from 65% to 85% for most beer styles. Higher attenuation means a drier, less sweet beer.
How many calories are in homebrew beer?
Calories in beer come from both alcohol and residual carbohydrates. A typical 5% ABV beer has roughly 150-180 calories per 330ml serving. Higher ABV and higher final gravity both increase calorie count.
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