Fermentation Timeline Calculator
Enter your yeast strain, starting gravity, and fermentation temperature to see predicted final gravity, ABV, a day-by-day gravity curve, and the best window for dry-hop or other additions. Nothing uploaded.
Yeast & gravity
Daily gravity curve
How fermentation timeline prediction works
Using yeast strain and temperature to predict days to terminal gravity
Each yeast strain ferments at different rates and has different limits on how much sugar it can consume (attenuation). The calculator uses yeast parameters: US-05 has a base duration of 7 days and 78-82% attenuation; W34/70 lager is 14 days and 74-79% attenuation. Temperature modulates fermentation speed: yeast works fastest near its optimal range, and slows dramatically above and below it. Example: US-05 at its optimal 66-70°F takes about 7 days to reach terminal gravity. At 50°F it takes 10-12 days (yeast works slower in cold). At 75°F it takes 5-6 days (yeast works faster). The calculator multiplies the base duration by a temperature factor to predict your specific fermentation timeline. Starting gravity (OG) does not change duration much - higher OG takes slightly longer, but the difference is smaller than temperature effects." }
The dry-hop timing window and why it matters
Dry hopping (adding hops during fermentation) is best done when fermentation is slowing but yeast is still active. If you add hops while fermentation is violent, yeast activity will blow off delicate hop aroma compounds as CO2 escapes. If you wait until fermentation is completely done, some aroma is lost to oxidation and time. The sweet spot is the window from 50% to 85% gravity drop. Example: OG 1.050, predicted FG 1.010 means a 40-point gravity drop. 50% is 1.030, 85% is 1.012. If fermentation timeline predicts day 3 at 1.030 and day 7 at 1.012, dry hop between days 3-7. The calculator shows this window in days." }
FAQ
What is attenuation and how does temperature affect it?
Attenuation is the percentage of sugars the yeast consumes during fermentation. Higher attenuation means the yeast eats more sugar, leaving less residual sugar (the final gravity will be lower, the beer drier). US-05 ale yeast has 78-82% attenuation. Champagne yeast has 85-90% attenuation (very aggressive). Temperature affects attenuation because yeast metabolizes faster when warm. US-05 at 68°F (optimal) reaches 80% attenuation; at 50°F it may only reach 75%. The calculator uses your actual temperature to predict realistic attenuation for your yeast and then calculates FG (final gravity).
How is fermentation duration calculated?
The calculator starts with each yeast's base duration (US-05 is 7 days, lager is 14 days). It then adjusts for temperature: fermentation speeds up near optimal temperature and slows down as temperature drifts away from optimal. Example: US-05 at its optimal range (65-69°F) takes about 7 days. At 50°F it takes roughly 10-11 days. At 75°F it takes roughly 5-6 days. The calculator shows a gravity curve with day-by-day predicted gravity, so you can see when fermentation is likely 50%, 75%, and 90% complete.
When should I add dry hops?
Dry hop during the phase when gravity has dropped to 50% of the distance from OG to FG (halfway point) through 85% of the way. This is the 'clean up' phase when yeast is still active but fermentation is slowing, so hop aroma compounds don't get blown off by vigorous CO2. Example: if OG is 1.050 and FG will be 1.010, the dry-hop window is from 1.030 to 1.012 gravity. The calculator shows this window in days.