How long will it take for my ale to ferment?

There are several variables that will impact rate of fermentation:
  1. Quantity and health of yeast pitched: A healthy yeast population will ferment more quickly than a weak yeast population
  2. Temperature: Warmer temperatures within the yeast’s optimum fermentation range will expedite fermentation
  3. The specific gravity of the wort: Higher gravity beers will take longer to ferment
  4. Proper Oxygenation/Aeration of cooled wort: Without proper aeration, yeast will not be able to reproduce, which stifles fermentation

One can expect the fermentation of most ales to be complete within two weeks. However, fermentation is a natural process and is therefore variable. It's quite possible that fermentation could take only 3 days or as long as 3 weeks.