As yeast converts sugar into alcohol, the liquid becomes less dense; the drop in specific gravity reveals the alcohol produced.
How to use the ABV Calculator
- Original gravity (OG)
- Final gravity (FG)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Subtract final gravity from original gravity and multiply by 131.25.
Inputs explained
| Field | What to enter |
|---|---|
| Original gravity (OG) | A number |
| Final gravity (FG) | A number |
What each result means
- Alcohol by volume = ([Original gravity (OG)] – [Final gravity (FG)])×131.25
- Apparent attenuation = ([Original gravity (OG)] – [Final gravity (FG)])÷([Original gravity (OG)] – 1)×100
Formula
ABV ≈ (OG − FG) × 131.25Worked example
Inputs — Original gravity (OG): 1.05; Final gravity (FG): 1.01.
Results — Alcohol by volume = 5.25 %; Apparent attenuation = 80 %.
Frequently asked questions
Is the formula exact?
It is accurate for typical beers; high-gravity brews need a more advanced formula.
Do I need to correct for temperature?
Yes, hydrometers are calibrated for a specific temperature, often 20 °C.
What formula does the ABV Calculator use?
ABV ≈ (OG − FG) × 131.25.