How Long to Ferment Beer

Homebrewers are notorious for wanting to have their beer finished fermenting and ready to drink as quickly as possible. This is why all of the instructions that come with the malt extract kits tell you to ferment for 7 – 10 days. They know you want to pop the top on that beer bottle as fast as possible. But the difference between making ok-tasting beer and making good quality beer is knowing exactly how long to ferment beer for and not rushing it.

Even experienced brewers will wrestle with wanting to get to the finished product as fast as possible, however with experience comes wisdom. I have learned over the years that developing patience and letting the yeast have the time it requires to do all of the work it is designed to do during the fermentation process will result in a much higher quality of beer that is worth the wait.

The short answer to how long it takes to ferment beer is 4 – 5 days. Within this time period, the yeast will have converted the majority of the sugars over to alcohol. But this does not mean you should rack your beer over to bottles or a keg just yet, the yeast still has more work to do to include finishing converting all of the sugars to alcohol and cleaning up the byproducts and off-flavors this process has created.

On average you should ferment most beers for 2 weeks then cold crash for 2 days before bottling or kegging. I say on average because fermentation time does vary depending on what type of beer you are brewing and how much you want to dial the process in.

Different Fermentation Times 
Pint opf beer sitting on wooden ferementer and the words how long to ferment beer written to the left of the beer.
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The first thing to understand is that there is a major difference in fermentation times and the processes involved between brewing Ales vs Lagers. In general, ales can be fermented at room temperature and within 2 weeks, whereas lagers require much colder temperatures typically in the range of 45 – 55 degrees Fahrenheit.

Due to the lower temperature requirement, fermentation in lagers is slowed down significantly. It is very common for lagers to take 6 – 8 weeks to fully ferment. For this reason, most homebrewers start out making ales. However, if you do wish to brew a lager I recommend you take the time to fully understand the difference between ales and lagers.

Fermentation time can also vary slightly between different styles of ales depending on the color of the beer itself. Lighter color ales such as a blonde, kolsch, or cream ale require less time to condition and mellow out.

Whereas darker beers do well when given more time to ferment. This is due to the darker roasted grains used to brew them which can produce harsh off-flavors. The more time you allow them in the fermenter the more these harsher flavors are going to mellow out and improve the taste of the beer.

In most cases, with lighter beers, 2 weeks is a perfect amount of time in the fermenter. For beers such as ambers and reds as well as stouts and porters an additional week in the fermenter will significantly improve their taste.

How Long to Leave Beer in Primary Fermenter

This leads to the next highly debated topic in homebrewing. How long should I leave the beer in the primary fermenter before racking to the secondary fermenter?

My answer to this question is do not bother racking to a secondary fermenter. In my opinion, there is no valid reason to do so, and there is a significant risk of infection if you do.

Many traditional brewers rack to a secondary as that was how they were taught. They believe the beer will clear up and condition better off the yeast cake. They also have concerns that leaving the beer on the yeast cake in the primary will result in off-flavors, they believe this happens due to a reaction called autolysis.

Autolysis is where the dead yeast cells rupture and create off-flavors. This concern has been debunked many times. As long as you control your fermentation conditions and don’t allow for extreme temperature changes you can leave your beer on the yeast cake for much longer than the 2 – 4 weeks it takes to fully ferment an ale.

My major concern with racking to a secondary besides the extra work involved is the high risk of oxygenating your beer. Oxygen at this stage of the brewing process is bad for your beer, it creates off-flavors and infections that can ruin your whole batch of beer.

So the short answer is to leave your beer in the primary fermenter until it is done fermenting, then cold crash it for 2 days followed immediately by bottling or kegging it.

How Do I Know When My Beer is Done Fermenting?

If you wait the 2 weeks your beer is going to be done fermenting. However, you can and should take gravity readings using your hydrometer. Your recipe will tell you what your final gravity should be. As you get close to the 2-week mark you can start taking gravity readings on a daily basis. If the gravity does not move for 2-3 days in a row then you know the beer is done fermenting.

However just because it has finished fermenting remember this does not mean it has finished conditioning.  Depending on the style of the beer as we talked about, give it the full 2-3 weeks to mellow out and improve its taste.

To improve your brewing skills, get in the habit of taking a sample and tasting the beer as it conditions, you should be able to detect an improvement in taste every day or two.

Frequently Asked Questions

Can you let beer ferment too long – The problem with letting beer ferment too long is you run the risk of oxygen getting into the fermenter and causing an infection. During active fermentation one of the byproducts created by the yeast converting the sugars is CO2. This gas creates a barrier between the beer and the oxygen, protecting it from becoming oxygenated.

When fermentation slows down and comes to an end the CO2 barrier starts to dissipate resulting in oxygen now being able to penetrate the beer. I get very worried this will happen as I get close to the 4-week mark, my recommendation is to never let your beer ferment for any longer than 4 weeks. (And I would rarely ever let it go that long)

One exception to this is if you engage in pressure fermentation where you are fermenting in a pressurized container and oxygen can not get in.

Can beer ferment in 5 days – Yes you absolutely can and I have many times in the past. In fact, I used to pride myself that I would be able to go from grain to glass in 5 days. If you take a gravity reading at day 5 you are going to see that in most cases you are very close to your final gravity.

However, as you mature as a brewer and get experience you come to appreciate that the conditioning phase of the fermentation process is just as important as getting to your final gravity reading. The only time I would now ferment in 5 days would be if I was in a rush to get some beer on tap.

How do I ferment beer – The basics of fermenting beer involves simply taking your finished wort, adding it to a fermenter and pitching your yeast into it. Then place the airlock filled with sanitizer, water, or vodka into the top of the fermenter and putting it in a location in your home that is within the temperature range indicated on the back of the yeast sachet, typically between 60 – 75 degrees Fahrenheit. Check out the following post to learn the exact process of fermenting beer.

There you have it, my friend, let me know in the comment section below if you have any questions about what we covered here today.

And if you are an experienced brewer let us know how long you typically ferment for?

Cheers, Big Robb is Out!

Big Robb with a pint of home brewed beer
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P.S. For a limited time I am giving away my top 5 recipes for my best-selling beers from my brewpub. You can sign up to get them on the side of the blog or at the bottom on a smart device. Enjoy!

2 thoughts on “How Long to Ferment Beer”

  1. Great article. Thanks. Just started my first “from scratch” brew and your article is very useful.

    • Right on Mark, glad to help man. Let us know how you make out! Cheers


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