Ovulation Calculator
Enter the first day of your last period and your cycle length to find your fertile window — the 5 days before ovulation plus ovulation day, when conceiving is most likely. Ovulation usually lands about 14 days before your next period.
How the fertile window works
An egg lives less than 24 hours after release, but sperm can survive in the body for up to 5 days. That is why the fertile window spans about 6 days: the 5 days leading up to ovulation plus ovulation day itself. Having intercourse in the 2 to 3 days before ovulation gives the best odds.
This tool assumes ovulation about 14 days before your next period. If your cycles are irregular, the calendar estimate is rougher, and watching for egg-white cervical mucus or using an ovulation predictor kit will pinpoint your window better.
Related questions
- When am I most fertile?
- The 2 to 3 days right before ovulation, plus ovulation day, are the most fertile. This tool marks that window from your cycle. Cervical mucus that looks clear and stretchy, like raw egg white, is a strong real-time sign you are approaching it.
- How many days is the fertile window?
- About 6 days: the 5 days before ovulation plus ovulation day. This reflects sperm surviving up to 5 days while the egg lasts under a day.
- Is this reliable for avoiding pregnancy?
- Calendar estimates alone are not reliable birth control because ovulation timing varies. If you are trying to avoid pregnancy, use a proven contraceptive method and talk with your provider.
Sources & further reading
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ParentFlow is a free baby tracker that logs feeds, sleep, diapers, pumping and growth in one tap, with your daily summary, trends, and reminders based on your own logs. Free for everyday tracking on iPhone, Android, and the web.
App Store Google Play Open Web AppThis tool gives general estimates for education only and is not medical advice or a diagnosis. Cycles vary month to month, so treat the window as an estimate; ovulation tests and cervical mucus track it more closely. For your own care, contact your healthcare provider.