Calculator

ABV Calculator

Enter your gravity before and after fermentation and it tells you how much alcohol your beer has and how much work the yeast has done.

Before you pitch the yeast.

When fermentation is done.

—ABV

— apparent attenuation

ABV Calculator: how to use it

  1. Take your original gravity (OG) with the hydrometer right before you pitch the yeast, once the wort has cooled.
  2. When fermentation is finished (the gravity hasn't changed for three days in a row), take your final gravity (FG).
  3. Enter them here: 1.050 or just "50" both work.

How it works

Yeast turns the sugar in the wort into alcohol and CO₂, and since alcohol is lighter than water, the gravity drops. The difference between original and final gravity tells you how much sugar the yeast has eaten: multiply it by 131.25 and you get alcohol by volume. It's a very good approximation up to about 8%; for very strong beers it reads a little low. Apparent attenuation is the percentage of the sugar that has disappeared: 70–80% is normal for almost every ale yeast.

Frequently asked questions

Can I use a refractometer for final gravity?

Not directly: alcohol skews the refractometer reading and makes it read high. Use a hydrometer for final gravity, or correct the reading with a correction formula.

What temperature should I measure at?

Whatever temperature your hydrometer is calibrated for, usually 20 °C (68 °F). Warmer wort reads low; if you can't cool the sample, correct the reading with your hydrometer's table.

How much alcohol does a typical beer have?

A commercial lager is around 4.5–5.5%. Below 4% it's a light beer, and above 8% it's a strong beer.

Why doesn't my beer get down to 1.000?

Because not all the sugar in the wort is fermentable: some stays unfermented and gives the beer body. Finishing between 1.008 and 1.015 is normal, higher the more crystal malt you use and the hotter you mash.