Ovulation Calculator
Enter your last period date and cycle length to find your fertile window and best days to conceive
Your Fertility Windows
- Estimated ovulation day:
- Implantation window:
- Next period expected:
- Earliest reliable pregnancy test:
How the Fertile Window Works
Ovulation usually happens about 14 days before your next period — not 14 days after the last one. Because sperm survive up to 5 days but an egg only 12–24 hours, your best chance of conception is the 5 days before ovulation plus ovulation day itself.
If your cycles are irregular (varying by more than 7 days), calendar methods become unreliable — ovulation predictor kits, basal body temperature or an ultrasound follicle scan give better answers. Persistent irregularity can signal PCOS or thyroid issues worth checking before fertility treatment.
Ovulation calculator FAQ
How do you predict ovulation?
Ovulation is typically about 14 days before your next period, so we estimate it from cycle length.
When is the fertile window?
The ~6 days around ovulation (about 5 days before through 1 day after).
My cycle is irregular — what now?
Predictions are less reliable; ovulation tests or a doctor's review can help.