What is Ovulation?
The Ovulation Calculator predicts when you are most likely to ovulate and your fertile window — the days when conception is most likely. This is the most important tool for couples trying to conceive (TTC).
Ovulation typically occurs 14 days before the start of your next period (not 14 days after your last period — this is a common misconception). For a 28-day cycle, ovulation is around day 14. For a 32-day cycle, it's around day 18. For a 26-day cycle, it's around day 12.
The fertile window spans approximately 6 days: 5 days before ovulation (sperm can survive up to 5 days) and the day of ovulation itself (the egg survives 12-24 hours). The two most fertile days are the day before and the day of ovulation.
For best chances of conception: have intercourse every 1-2 days during your fertile window. You don't need to pinpoint the exact ovulation day — covering the window is sufficient.
Formula
Ovulation Day = Last Period Date + (Cycle Length − 14)
Fertile Window = Ovulation Day − 5 to Ovulation Day + 1
Next Period = Last Period + Cycle Length
Example — LMP March 1, 28-day cycle: Ovulation = March 1 + (28−14) = March 15 Fertile window: March 10 − March 16 Next period: March 29
For 32-day cycle: Ovulation = March 1 + 18 = March 19 Fertile window: March 14 − March 20
How to use this Ovulation Calculator?
1. Enter the first day of your last menstrual period. 2. Enter your average cycle length (count from day 1 of one period to day 1 of the next). 3. See your predicted ovulation date, fertile window, and next period date.
Note: This works best for regular cycles. If your cycle varies by more than 7 days, consider ovulation predictor kits (OPKs) or basal body temperature tracking for more accuracy.