How is the alcohol content of beer calculated?

The most common formula is: (OG − FG) × 131.25 / 1000. OG is the original gravity before fermentation and FG is the final gravity after it. The difference shows how much sugar was turned into alcohol.

OG (Original Gravity) is the density of the wort before fermentation, e.g. 1.050. FG (Final Gravity) is the density after fermentation, e.g. 1.010. Both are measured with a hydrometer.

What is a good attenuation?

Typical attenuation is 70–80%. It tells you how much of the sugars the yeast converted into alcohol. A higher rate gives a drier and stronger beer.

Is there a difference between ABV and ABW?

ABV (Alcohol By Volume) is the percentage by volume — the most common way of labelling. ABW (Alcohol By Weight) is the percentage by weight, which is about 0.79 × ABV. Finland uses ABV.

ABV Calculator — Homebrew Alcohol Content

Calculate the alcohol content (ABV) of your homebrew from original and final gravity (OG/FG). Free ABV calculator.

Alkupaino OG: 1,050

Loppupaino FG: 1,010

Erän koko: 20 litraa

5.3 %

Alkoholiprosentti (ABV)

ABV (tilavuusprosentti)	5.25 %
ABW (painoprosentti)	4.15 %
Käymisaste	80 %
Vakioannoksia erässä	69 annosta

ℹ️ ABV-kaava: (OG − FG) × 131,25 / 1000. OG = vierteen alkupaino ennen käymistä, FG = loppupaino käymisen jälkeen. Mittaa hydrometrilla. Käymisaste kertoo kuinka paljon sokerista muuttui alkoholiksi.

This homebrew calculator works out the alcohol content of your beer or cider from the original and final gravity. Alongside ABV you get the alcohol by weight, the apparent attenuation and an estimate of the standard drinks in your batch — a handy tool for every home brewer.

How the calculator works and what it’s for▾

How ABV is calculated

The calculator uses the common formula (OG − FG) × 131.25 / 1000, where OG is the gravity of the wort before fermentation and FG is the gravity after it. Measure both with a hydrometer.

For example, if OG is 1.050 and FG is 1.010, the difference is 40 points and the result is roughly 5.3 % ABV.

What you enter and what you get

Enter the original gravity (OG), the final gravity (FG) and the batch size in litres. From these the calculator derives every result.

You get alcohol by volume (ABV), alcohol by weight (ABW), the attenuation and an estimate of how many standard drinks the batch contains.

What attenuation tells you

Attenuation shows how much of the sugar in the wort was converted into alcohol during fermentation. A high attenuation means a drier, stronger finished drink.

A low final gravity relative to the original gravity indicates a more complete fermentation.

Measuring tips

Read the hydrometer at eye level and account for temperature correction, since measurement accuracy directly affects the result. Record OG just before pitching the yeast and FG only once fermentation has stopped.

🔄 Reviewed June 2026