I see fermentation duration questions a lot in forums and homebrewing Facebook groups. It’s not necessarily a one-size-fits-all answer, but there are simple guidelines to follow, especially if you want to err on the side of caution. Beer fermentation time is largely dependent on the beer style. Just to preface this article, a beer’s time to ferment versus time spent in a fermentation vessel are two separate questions with different answers.
The short answer: Although most ales ferment in 2-5 days, I always recommend you wait at least 2 weeks before moving to bottles/kegs for the best results. Lagers on the other hand ferment in 2-3 weeks followed by several weeks or even months to condition.
Lagers require a much more rigorous and extended fermentation schedule. Lagers also ferment at much cooler temps (45-55°F.) I’ll be honest, I’ve never actually brewed a lager because I don’t really drink them. That being said, a general guideline is usually 2-3 weeks for primary fermentation followed by several weeks or even months of cold conditioning/lagering in a secondary vessel. The whole process takes about 2-3 months, depending on the style. This article dives into more details on lager fermentation.
How Long Should Beer Stay in the Primary Fermenter?
As I mentioned, your typical ale ferments in 2-5 days at a recommended temperature range of 62-75°F (I prefer the lower end for cleaner results). The active fermentation process is actually pretty quick (especially at warmer temps). It’s the conditioning/secondary phase that is equally important and usually takes much longer.
I no longer use a secondary fermenter for ales (you can read more about this here). I usually keep my ales in the primary fermenter for a total of 2-3 weeks before cold crashing and kegging. This completely ensures that fermentation has fully completed AND the yeast has had a chance to clean up unwanted byproducts produced by fermentation. This is also usually ample time for sediment to fall out of suspension and clear up the beer.
Check The Final Gravity
Most finished beers will have a final specific gravity of 1.010-1.020. Use your hydrometer to take a final gravity reading to see if it has completed fermentation. In most cases, your recipe will give you a ballpark figure of where your beer’s final gravity will fall. If your beer reads at FG or very close, then your beer has completed the vast majority of fermentation. That being said, just because a beer has finished fermenting, doesn’t mean it’s finished conditioning.
If you carefully taste your beer as it progresses through conditioning, you will notice a gradual improvement over the course of 2 weeks. By day 14, most if not all harshness and off-flavors you tasted early on will have mellowed or be rendered undetectable. I think this is a valuable exercise for beginners. Just be careful about sanitizing anything you put in your fermenter to take samples. Ideally, you should pull a small sample via a spigot on the fermenter to prevent opening or oxidation.
Risks of Racking/Transferring Too Early
The conditioning phase of fermentation allows your yeast to finish the job and clean up the mess. Yeast produces undesirable byproducts as a result of primary fermentation. Once this process has completed, they turn their attention to reabsorbing some of these produced off-flavors. Racking too early can disrupt this process or potentially stall fermentation. You could also place unwanted stress on the yeast during this phase if you remove the beer from the yeast cake too soon.
I still fight the temptation to keg my beer early but it’s SO important to be PATIENT.
As you get more experienced, you’ll have a better idea of when your beer is ready to be consumed. Commercial breweries have tremendous experience with this and also brew a lot of the same beers over and over again, so they have their process down to a literal science.