ABV Calculator
Enter your original gravity (OG) and final gravity (FG) readings to find your brew's alcohol by volume.
How ABV is calculated from gravity readings
This calculator uses the standard homebrewing formula ABV% = (OG − FG) × 131.25, where OG and FG are specific gravity readings taken before and after fermentation with a hydrometer or refractometer.
The difference between the two readings reflects how much sugar the yeast converted into alcohol during fermentation — a bigger drop in gravity means more sugar was consumed, and generally more alcohol was produced.
Frequently asked questions
What are OG and FG?
Original gravity (OG) is the specific gravity of your wort or must measured before fermentation begins; final gravity (FG) is measured after fermentation is complete. Both are typically read with a hydrometer, usually in the range of 1.000 to 1.120.
Is this formula accurate for all beverages?
This simplified formula is widely used by homebrewers for beer, wine, and cider and is accurate enough for most hobbyist purposes. More precise formulas exist that account for the nonlinear relationship between gravity and alcohol at higher ABVs, used mainly for very strong brews.
Why might my calculated ABV seem off from what I expected?
Temperature affects hydrometer readings — most hydrometers are calibrated for a specific temperature (often 60°F/15.6°C), so readings taken at a different temperature need a correction factor for an accurate result.