Final gravity, or FG, is the reading once fermentation has finished. It tells you the beer is done and, with your OG, gives you the ABV. A warm sample reads low, so correct it below before you trust it.
Correct your final gravity
Knowing when fermentation is done
Take two final gravity readings two or three days apart. When the number stops moving, fermentation is finished and the beer is ready to package. Correct each reading for temperature so a warm sample does not trick you into bottling early.
Bottling on a false-low FG is a classic cause of over-carbonation and gushers, because there is still fermentable sugar left to react with your priming sugar.
What a normal FG looks like
Most beers finish between 1.008 and 1.015 depending on the recipe and yeast. Dry styles can drop below 1.008, while sweeter or higher-mashed beers finish higher.
Pair your corrected FG with your OG in the ABV calculator to get your alcohol figure, and check apparent attenuation there as a sanity check on the ferment.
Frequently asked questions
How do I know fermentation is finished?
Take two final gravity readings two or three days apart. When the number stops moving, fermentation is done. Correct each reading for temperature so a warm sample does not fool you into bottling early.
What is a normal final gravity?
Most beers finish between 1.008 and 1.015 depending on the recipe and yeast. Very dry beers can go below 1.008; sweeter or higher-mashed beers finish higher.
Why correct FG for temperature?
The same reason as any hydrometer reading: a warm sample reads low. If you bottle on an uncorrected warm FG you can misjudge attenuation and, with priming sugar, risk over-carbonation.
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