Homebrew ABV Calculator
Alcohol by volume from original and final gravity.
Enter your values
Enter the original gravity you are working with.
Enter the final gravity you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- ABV (standard formula)
- 5.25%
- ABV (high-gravity formula)
- 5.34%
- Apparent attenuation
- 80%
Quick answer
ABV is calculated from the drop in specific gravity between the original and final readings during fermentation.
ABV% = (OG - FG) x 131.25
At a glance
| What it does | Alcohol by volume from original and final gravity. |
|---|---|
| Category | Everyday |
| Inputs needed | Original gravity, Final gravity |
| Main output | ABV (standard formula) |
| Formula | ABV% = (OG - FG) x 131.25 |
| Cost | Free — no sign-up, no download |
How to use the Homebrew ABV Calculator
- 1Take an original gravity (OG) reading before fermentation begins.
- 2Take a final gravity (FG) reading once fermentation has finished (stable reading over a few days).
- 3The standard formula works well for most beers; use the high-gravity formula for strong beers/meads above ~1.070 OG.
Inputs explained
- Original gravity
- Enter the original gravity you are working with.
- Final gravity
- Enter the final gravity you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Original gravity1.050
- Final gravity1.010
Results
- ABV (standard formula)5.25%
- ABV (high-gravity formula)5.34%
- Apparent attenuation80%
Frequently asked questions
Why two ABV formulas?
The standard linear formula loses accuracy at higher gravities, so a more precise formula is used for strong brews.
What if my FG reading is still dropping?
Wait until it's stable for 2-3 consecutive days before taking your final reading to avoid bottling too early.
What do I need to enter into the Homebrew ABV Calculator?
Just 2 values: original gravity, final gravity. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Homebrew ABV Calculator work out the answer?
ABV is calculated from the drop in specific gravity between the original and final readings during fermentation. It applies the formula ABV% = (OG - FG) x 131.25 and shows the working so you can check each step by hand.
Is the Homebrew ABV Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.