ABV Calculator
Enter your original and final gravity readings to estimate the alcohol by volume of your home brew — and see how the gravity drop becomes a percentage of alcohol.
Two readings, one number
Enter the original gravity (before fermentation) and the final gravity (after) and the calculator returns the alcohol by volume in percent.
Gravity must fall
The final gravity has to be at or below the original gravity — the reading drops as yeast turns sugar into alcohol.
What does this ABV calculator do?
From gravity readings to alcohol percentage
This ABV calculator estimates the alcohol by volume of a fermented beverage from two hydrometer readings: the original gravity taken before fermentation and the final gravity taken after. As yeast eats the sugar in your wort or must and produces alcohol, the liquid becomes less dense and its specific gravity falls. The size of that drop tells you how much sugar was converted, and therefore roughly how much alcohol was produced. Enter both readings and the calculator turns the gap into a percentage using the standard homebrewing formula — the same number a brewer writes on the label of a finished batch.
Enter your original gravity and final gravity to get the alcohol by volume of your batch instantly.
The alcohol by volume is the difference between the original and final gravity, multiplied by the standard factor 131.25.
ABV = (OG − FG) × 131.25The gravity drop (OG − FG) measures how much dissolved sugar disappeared during fermentation, and the factor 131.25 converts that drop into a percentage of alcohol. The bigger the gap between the two readings, the more sugar the yeast fermented and the stronger the result.
Suppose your beer started at an original gravity of 1.050 and finished at a final gravity of 1.010.
Find the gravity drop
1.050 − 1.010 = 0.040 — how far the specific gravity fell during fermentation.
Multiply by 131.25
0.040 × 131.25 = 5.25 — the gravity drop converted to a percentage.
Read the result
The beer is about 5.25 % ABV — a typical strength for a standard ale or lager.
The percentage tells you how strong the finished beverage is. Gravity falls as fermentation proceeds because yeast consumes the dense sugar and replaces it with lighter alcohol, so a larger drop between your two readings means more sugar was converted and a higher ABV. Most everyday beers land between 4 % and 6 % ABV: light lagers sit nearer 4 %, many ales and pilsners around 5 %, and stronger IPAs or doubles climb to 7 % and beyond. Wine typically reaches 11–14 %, which comes from a much larger starting gravity. If your final gravity has stopped falling over several days, fermentation is finished and the number you see is your real strength; if it is still dropping, the ABV will keep rising until the yeast runs out of sugar.
The formula is a trusted shortcut, but a couple of practical points are worth keeping in mind.
A standard approximation, best below 8 % ABV
The × 131.25 factor is a standard linear approximation. It is reliable for typical beers up to roughly 8 % ABV, but above that it overstates the result, and brewers switch to more detailed equations. Take both hydrometer readings at the calibration temperature and correct for any difference, since temperature shifts the gravity — and remember the final gravity must be at or below the original gravity, because the reading can only fall as sugar ferments to alcohol.