Ovulation Calculator
Calculate your ovulation date and fertile window to plan or track pregnancy.
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Ovulation Date
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Enter your date
How Ovulation Works
Ovulation is when a mature egg is released from the ovary, typically 14 days before your next period. The egg survives 12–24 hours, while sperm can live up to 5 days in the reproductive tract — creating a ~6-day fertile window.
Ovulation Day = Cycle Length − 14
Fertile Window = Ovulation − 5 days to Ovulation + 1 day
Fertile Window = Ovulation − 5 days to Ovulation + 1 day
Fertility by Cycle Length
| Cycle Length | Ovulation Day | Fertile Window |
|---|---|---|
| 21 days | Day 7 | Days 2–8 |
| 28 days | Day 14 | Days 9–15 |
| 30 days | Day 16 | Days 11–17 |
| 35 days | Day 21 | Days 16–22 |
Disclaimer: Estimates only, not medical advice. Consult a healthcare provider for fertility concerns.
Frequently Asked Questions
How do I calculate my ovulation date?
Ovulation typically occurs 14 days before your next period. For a 28-day cycle, ovulation is around day 14. The fertile window is the 5 days before ovulation plus ovulation day.
What is the fertile window?
The fertile window is the 6 days leading up to and including ovulation. Sperm can survive up to 5 days, and the egg lives 12–24 hours, so conception is possible during this window.
How accurate is ovulation calculation?
Calendar-based ovulation prediction is about 75% accurate for regular cycles. Irregular cycles make prediction harder. Ovulation test kits and basal body temperature tracking are more accurate.
When am I most likely to get pregnant?
The 3 days leading up to ovulation and ovulation day itself have the highest pregnancy probability. The day before ovulation has the highest chance at about 30%.