How long should primary fermentation last?

Most ales finish primary in 7-14 days at 18-22°C. Lagers take 14-28 days at 10-14°C. High-gravity beers (OG above 1.070) may need 2-4 weeks. Always verify with stable gravity readings over 3 consecutive days rather than relying on time alone.

Do I need secondary fermentation?

Most standard ales do not benefit from secondary. It is useful for lagers (extended cold conditioning), high-gravity beers (bulk ageing), and beers with additions (fruit, dry hops). For most homebrews under 1.060 OG, leaving in primary for the full duration is preferred.

How does temperature affect fermentation time?

Higher temperatures speed up fermentation but can produce off-flavours (fusel alcohols, esters). Lower temperatures slow fermentation but often produce cleaner results. Lagers fermented at 10-12°C take roughly twice as long as ales at 18-20°C.

How do I know when fermentation is complete?

Take hydrometer readings on consecutive days. When the reading is stable (within 0.001) for 3 days, fermentation is complete. Airlock activity alone is not reliable — CO2 can continue escaping long after fermentation finishes.

How do I know when primary fermentation is done?

Take hydrometer readings on consecutive days. When gravity is stable for 2-3 days and has reached the expected FG, primary is complete. Do not rely solely on airlock activity — it can stop while fermentable sugars remain.

BrewCalcs

Fermentation Time Calculator

Estimate primary and secondary fermentation duration for your beer.

Original Gravity (OG)

Starting gravity of your wort

Expected Final Gravity (FG)

Fermentation Temperature

Beer Type

How We Calculate This

Estimating Fermentation Time

Primary duration is estimated from the gravity drop (OG - FG) scaled by beer type and temperature. Larger gravity drops and lower temperatures increase the time. The formula uses a base duration for each style, multiplied by gravity and temperature adjustment factors.

Secondary Duration

Lagers benefit from extended cold conditioning (lagering) at near-freezing temperatures. High-gravity beers benefit from bulk ageing. Standard ales typically need no secondary unless adding ingredients like fruit or dry hops.

Frequently Asked Questions

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Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.