When to Bottle Beer & What Happens if done Wrong!

You’ve gone through all the different steps of the brewing process and now your beer is sitting in the fermenter, but you’re still wondering when to actually bottle it, if doing it too early or too late could cause any problems, how to actually know when it’s time to bottle, if you can do it straight from the primary fermenter or if you absolutely have to transfer it to a secondary fermenter or to a bottling bucket for that matter, and more.

In this article, I will go over when you should bottle beer, as well as provide you with some information about how fermentation works since it’s essentially what determines when it’s time to bottle your beer, the issues that could arise if you bottle too early or too late, and more.

So, without any further ado, let’s get started.

When to Bottle Beer

bottles, beer bottles, bottle caps

Knowing when to bottle beer depends entirely on the fermentation process and if it is complete or not, and I will explain this in detail in the next two sections, but if you just want a quick rundown of the usual timeframes, then here’s the short answer:

Ale beers usually require from 4 to 7 days until primary fermentation is complete and then another two weeks in secondary fermentation (depending on the style) to be ready to bottle, whereas Lagers generally require around 14 days in primary fermentation and then 4-6 weeks in secondary in order to be ready for bottling.

Important: This is a very simple guideline since fermentation doesn’t always take the same amount of time to complete and you shouldn’t base your decision on time but rather take hydrometer readings to make sure that fermentation is no longer active.

Understanding Fermentation

Fermentation is when the yeast consume all of the available sugars to produce all the alcohol, aroma, and flavor compounds found in beer, and the temperature, oxygen levels, and pitch rate as well as yeast strain selection will all dramatically affect the production of aroma and flavor compounds produced during fermentation and, therefore, the overall taste of the beer.

If any of these factors are off, such as the temperature being too high, the chance of your beer having off-flavors is quite high, lowering the overall quality of the final product.

How to know if fermentation is complete?

Whenever you transfer your wort from the kettle into the fermenter it’s important to take a gravity reading, also known as Original Gravity (you can use a hydrometer or refractometer for this), since this will allow you to then calculate the alcohol content, or ABV, of your beer later on.

Then, once you pitched the yeast and a couple of days have passed, especially when you don’t see any Airlock activity anymore, you need to start taking gravity readings (one per day is recommended).

Note: No Airlock activity doesn’t necessarily mean that fermentation has stopped, it just means that it may not be as vigorous anymore but may still be ongoing.

If fermentation is still ongoing, then the gravity will keep on dropping every day, even if it’s just a little.

The way to be 100% certain that fermentation is complete is by taking two or three separate hydrometer readings each 24hs apart from the other and getting the exact same gravity each time. That’s when you know the yeast have completely consumed all of the available sugars and fermentation is complete.

Note: You can use a refractometer for this as well but you will need to make a small correction to get accurate results, which is why I’d recommend using a hydrometer if you’re just getting started.

How to get accurate Gravity Readings

  1. Take a big-enough sample from the fermenter to float the hydrometer (via the tap, don’t open the fermenter).
  2. Degas the sample by pouring it back and forth between cups (you can also use a cloth strainer/coffee filter).
  3. Repeat the process every 24 hours until two or three separate readings show the same gravity.

Recommendation: If you don’t want to waste a lot of your brew by taking multiple hydrometer readings since this requires you to take out a fairly large sample, then you can use a refractometer and take readings every day until the gravity stops dropping, and THEN you use the hydrometer to measure the final gravity.

Doing this will actually save you a good amount of beer, but remember that the refractometer won’t give you accurate readings unless you already calculated the correction factor of your refractometer and use that to get the final gravity.

What happens if fermentation didn’t finish and you bottle anyway?

When bottling beer, unless it’s already carbonated in a keg or if you fermented it under pressure, you always add priming sugar to the bottles or to the beer itself to reactivate the yeast so that they produce Co2 during bottle conditioning, and since the Co2 can’t get out of the bottle as it does through the airlock in the fermenter, it carbonates the beer.

If you decide to bottle while fermentation is still ongoing, there will still be fermentable sugars available for the yeast to consume, meaning that you won’t exactly know how much of the priming solution to add, and this results in an over carbonation of your beer which will most certainly cause gushing of beer when you open the bottles, and from personal experience, the gushing takes literal minutes to stop.

If for some reason there are too many fermentable sugars inside of the bottle and too much pressure starts to build up, the bottle might even burst, which is commonly referred to as “bottle bombs” (tried it but didn’t manage to get it to burst, only got a gushing beer).

This is why it’s extremely important to make sure that fermentation is 100% complete since otherwise, you won’t know how much priming sugar to add.

This, of course, begs the question of whether or not you can bottle directly from the primary fermenter and if secondary fermentation is actually needed.

Leaving the beer in the fermenter for too long

If you leave the beer to ferment longer, say an extra week or two, generally speaking, nothing bad is going to happen and it will allow the yeast to flocculate and clear up the brew further.

However, over time, the yeast cells die and they start to autolyze, essentially breaking apart, rupturing their cell walls, and introducing some off-flavors, such as broth-like, meaty, sulfur, and dirty diaper flavors, into the beer (people refer to it as the “smell of death”).

If you can smell sulfur, or any “dead” smell coming from the fermenter, then it’s probably because of autolysis and it’s best to throw the beer out and start fresh.

Can you bottle from the primary fermenter?

As long as fermentation is complete, you can bottle directly from the primary fermentation vessel.

The reason for doing a secondary fermentation is to let beer clear over that period of time by promoting the flocculation of yeast cells that are in suspension, and also to round out all of the flavors.

Depending on the style of beer you’re brewing, if it’s supposed to be crystal clear or not, you may want to transfer the beer to a secondary fermenter, or if you have a conical fermenter that allows you to remove all of the trub and yeast then you can do this in the same fermenter and leave it there for at least two weeks if it’s an Ale, and 6+ weeks if it’s a Lager.

Cold crashing your beer for three or four days before bottling will also promote the flocculation of the yeast and clear up the beer even further.

Now, if you can bottle straight from the primary fermenter or even from the secondary one, why do people use bottling buckets?

Do you need to use a bottling bucket?

Racking to a bottling bucket lets you fully mix the priming solution and the beer, allowing the yeast to carbonate your beer in the bottle later on. Another benefit of using a bottling bucket is that it helps clarify the beer since you move it away from the yeast that flocculated to the bottom of the fermenter.

During fermentation, the yeast multiplies and consumes the sugars until their lifecycle ends and they die. Once dead, and if left in the fermenter for too long, they start to autolyze, that is break apart, rupturing their cell walls, and this can introduce some off-flavors, such as broth-like, meaty, sulfur, and dirty diaper flavors into the beer.

Still, the main benefits of using a bottling bucket are the ability to mix the priming sugars with the beer itself by first pouring the primer into the bucket and then the beer on top of it, and to further help with beer clarification.

Note: When transferring beer into a bottling bucket make sure to do it slowly and not to splash as to not introduce any oxygen to prevent oxidation.

How to properly Bottle beer

Bottle conditioned beer

I wrote an entire guide on how to bottle beer correctly which you can find here, but I’d also recommend reading my entire guide on cleaning and sanitizing your bottles, as well as the rest of the equipment, in order to prevent contamination.

Here is a quick rundown of how to do it:

  • Have the necessary equipment ready to go and sanitized (Bottle filler, bottles, caps, capper, etc.).
  • Prepare the priming solution using 7 grams of dextrose per liter of beer.
  • Transfer the priming solution into the bottles using a syringe or pour it all into the bottling bucket (if using one).
  • Using a bottle filler, fill the bottles (or transfer the beer into the bottling bucket using a siphon and then fill the bottles from there).
  • Cap the bottles using the capper.
  • Store the bottles vertically in a dark place at room temperature.


As I mentioned, making sure that fermentation is complete is by far the most important factor to determine whether or not your beer is ready to be bottled, and that’s done by taking two hydrometer readings 24hs apart and getting the same gravity reading both times, that’s when you know the beer is completely fermented and you’re ready to bottle.

If you don’t want a gushing beer, or worse yet, beer bombs, then I’d recommend not bottling before fermentation is 100% complete.

By that same token, leaving the beer in the fermenter for too long will cause yeast autolysis (the yeast cells die and their walls burst), which will introduce really unpleasant off-flavors into the beer.

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