Ovulation Calculator
Predict your fertile window and next ovulation day from cycle length and the first day of your last period.
Days after ovulation before period; 14 is typical
Day 1 = first day of bleeding
Ovulation day (of cycle)
14
Breakdown
- Fertile window starts
- 9
- Fertile window ends
- 15
- Days until next ovulation
- 4
- Next period expected (cycle day)
- 29
- Status
- Ovulation in 4 day(s)
Last updated:
FAQ
Why is the fertile window 6 days?
Sperm survive up to 5 days inside the reproductive tract while the egg lives only 12–24 hours. Intercourse in the 5 days before ovulation plus ovulation day itself covers nearly all conceptions.
How reliable is cycle-day math?
It assumes your cycles are regular and your luteal phase is stable. Real ovulation shifts with stress, illness, and travel — ovulation predictor kits or BBT tracking confirm it directly.
Can I use this to avoid pregnancy?
No. Calendar prediction alone is one of the least reliable contraception methods because ovulation can move earlier without warning. Use it only as a fertility-awareness signal combined with stricter methods.
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