How Long to Ferment Beer? Your Quick Home‑Brewing Cheat Sheet

Wondering whether two weeks is enough for your ale? The answer isn’t one‑size‑fits‑all, but you can nail the right window by looking at the style, yeast, and temperature. Below we break down the basics so you can tell if your brew is ready or still needs a bit more time.

Typical Fermentation Windows by Beer Style

Most ales finish primary fermentation in 7‑14 days when kept between 65‑70°F (18‑21°C). Lagers need colder temps (45‑55°F or 7‑13°C) and usually take 2‑4 weeks for primary, plus another 2‑4 weeks in secondary. Stouts and high‑gravity beers often linger a bit longer—up to 3 weeks—because the yeast works harder to consume extra sugars.

Here’s a quick snapshot:

• Light ales (pale ale, blonde ale): 5‑10 days
• Medium ales (IPA, amber): 7‑14 days
• Strong ales (imperial, barleywine): 14‑21 days
• Lagers: 14‑28 days primary, plus 2‑4 weeks cold‑crash

Signs Your Beer Is Done Fermenting

Don’t just count days—listen to the airlock and check the gravity. When bubbling slows to a few drops per minute and a stable final gravity stays the same for three days, the yeast has likely finished its job. A quick hydrometer reading that matches your target FG (final gravity) is the safest green light.

If you’re still seeing a lot of activity after the expected window, consider these culprits:

• Temperature swings – cooler temps slow yeast, warmer temps can stress it
• Under‑pitching yeast – not enough cells to finish quickly
• High original gravity – more sugars mean longer work for the yeast

Adjusting any of these can help bring the timeline back on track for your next batch.

Bottom line: two weeks works for most ales at proper temperature, but always confirm with gravity and airlock activity. Letting beer sit a little longer can improve clarity and flavor, especially for stronger styles. Happy brewing!