So, I'm totally new to homebrewing. About to start my first brew, and it's a complete kit with instructions. Supposedly, it can't go wrong. BUT, it says that fermentation is over in 16 days. I assume this is not an exact number, so how can I tell, if it is done fermenting? Can the SG measurements tell me that?

Also, when it is done, will I need to bottle it immediately, or can it wait a day or two?

4 Answers 4


For a regular strength beer just leave it in the primary for 14-21 days and then bottle. When primary fermentation is coming to an end, the yeast turn to conditioning the beer, which removes the "green" taste from the beer.

If you want to take a gravity reading after a week then that's fine, but when brewing from a kit, I feel it's optional. I'd avoid opening the fermentor unnecessarily, and instead leave off taking a gravity reading until bottling time.


Sixteen days sounds about right (better than the 10 days some kits recommend). To be sure, you need to take gravity readings and get the same result for three days straight. With a kit, though, you're usually pretty safe to just follow the directions that came with it.

Once fermentation is done, the yeast will start to consume whatever fermentables they can get, which in most cases is some of the more complex sugars and fermentation by-products. The longer you leave the beer in the fermenter, the more yeast and trub will drop out of solution, leaving you with a clearer beer. Your beer should be fine for up to two months in the fermenter, so there's no hard deadline for bottling. Of course, after you bottle you have to wait a couple of weeks for the bottles to carb up, so the longer you wait the longer it'll be until you can drink!

  • Thanks! I'm sure the wait will be the hardest part. We will only need to push it one or two days, so hopefully we'll manage :)
    – Nicolai
    Oct 25, 2012 at 6:23

If it has an airlock, you can watch for bubbles stopping and slowing down to get a rough idea of when primary fermentation is slowing down and stopping. The best way though is to take a gravity reading. Once the gravity stays constant for a few days you'll know that primary is finished. Just be sure to sanitize when you are checking gravity.

No need to bottle immediately once fermentation is done. The beer will be fine for months. Many high ABV styles need to be aged for months long after primary fermentation is finished before they are ready. For lighter bodied or hoppy beers, you'll want to bottle sooner but waiting a day or two is perfectly fine.

  • If you plan on leaving the beer for more than a few weeks before bottling, you should rack to a carboy rather than leave it in the fermenting bucket. You need to exclude oxygen when aging beer. Oct 23, 2012 at 14:50
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    @TobiasPatton, shouldn't the oxygen be gone from the yeast consuming it and c02 blowing out the airlock? I'd think if anything racking would be more likely to introduce oxygen.
    – awithrow
    Oct 23, 2012 at 19:36
  • Good point. My fermentation buckets have loose fitting lids, so I forget that some people use tight lids and airlocks. Oct 26, 2012 at 18:24

Watch the airlock and when there seems to be no activity then take a gravity reading. If you are using a kit then you should have been given the final gravity (FG).

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