Estimate your fertile window and ovulation day, or switch to Cycle Tracker mode for a multi-month forecast of periods and fertile windows.
Cycle Estimate
--
Enter your last period date and average cycle length. Use Single mode for the next fertile window, or Cycle Tracker for a multi-month forecast.
Tap an example to prefill the calculator with sample values.
Typical 28-day cycle
LMP on March 1 with a 28-day cycle
A common planning estimate for a fairly regular cycle.
Result: The fertile window lands about two weeks before the next expected period.
Longer cycle
32-day cycle with a 6-day period
Useful when ovulation tends to happen later in the cycle.
Result: The fertile window shifts later because the expected next period shifts later too.
6-month forecast
Plan ahead with a 28-day cycle over 6 months
Use Cycle Tracker mode to see upcoming periods, fertile windows, and ovulation dates for the next 6 cycles.
Result: A 6-cycle forecast with predicted period dates, fertile windows, and ovulation days through August.