Calculate alcohol by volume for homebrewing from original and final specific gravity readings.
How It Works
How ABV Calculator (Alcohol By Volume) Works
As sugar ferments into alcohol, the liquid's density (specific gravity) drops — the difference between the original gravity (measured before fermentation) and final gravity (measured after) is multiplied by a standard constant to estimate the resulting ABV.
Worked Example
See It In Action
An original gravity of 1.050 dropping to a final gravity of 1.010 gives an estimated ABV of about 5.25%.
FAQ
Frequently Asked Questions
Why does a bigger gravity drop mean more alcohol?
The drop in gravity reflects how much sugar the yeast actually converted into alcohol and CO₂ — a bigger drop means more sugar was fermented, which means more alcohol was produced.
How accurate is this formula?
It's a widely used homebrewing approximation that's accurate enough for most beers and worked well within the OG range typical of standard-strength brews; specialized formulas exist for very high-gravity brews where this simpler version becomes less precise.
