How to use this calculator
Enter your original gravity (OG) reading taken before pitching yeast, and your final gravity (FG) reading taken after fermentation is complete. You can input values as specific gravity (e.g., 1.050) or in Plato/Brix degrees.
If your hydrometer reading was taken at a temperature other than 60°F, enable the temperature correction checkbox and enter the sample temperature. The calculator will adjust your gravity readings before computing ABV.
Understanding the results
The standard formula (OG − FG) × 131.25 works well for most beers. The alternate formula is more accurate for higher gravity beers above 6% ABV. Both are shown so you can compare.
Apparent attenuation tells you what percentage of sugars your yeast consumed. Higher attenuation means a drier, less sweet beer. The style range indicator shows where your ABV falls relative to common beer styles.
Frequently asked questions
What is original gravity?
Original gravity (OG) measures the density of your wort before fermentation. It tells you how much dissolved sugar is available for yeast to convert into alcohol. A typical OG ranges from 1.030 for light beers to 1.090+ for strong ales.
How do I measure gravity?
Use a hydrometer (floats in a sample and reads directly) or a refractometer (uses a few drops, reads in Brix). Take an OG reading before adding yeast and an FG reading when fermentation is stable for 2 to 3 consecutive days.
What is good attenuation?
Most ale yeasts achieve 72% to 82% apparent attenuation. Below 70% may mean a stalled fermentation. Above 82% is common with Belgian strains or recipes using simple sugars. Your target depends on the style you are brewing.
Why is my ABV low?
Low ABV usually means fermentation stopped early. Common causes: unhealthy or old yeast, temperature too low, insufficient oxygenation, or too many unfermentable sugars from high mash temperatures. If FG is higher than expected, try raising temperature slightly or adding fresh yeast.