Ovulation Calculator
Estimate your likely ovulation date from the first day of your last period and your average cycle length. Ovulation can vary, so treat the result as a window of possibility, not a certainty.
Your cycle details
Your estimate
Enter your cycle details to see an estimate.
How this estimate is calculated
The calculator projects your next expected period, then estimates ovulation as about 14 days before it. The fertile window is shown as the five days before ovulation through the day after.
This method assumes a relatively regular cycle and a luteal phase of about 14 days. Some people ovulate earlier or later, and the timing can differ from cycle to cycle.
For a closer look at calendar estimates and body signs, read ovulation signs and your fertile window.
What this tool cannot tell you
- Whether ovulation actually happened
- The exact day an egg was released
- Whether you can or cannot become pregnant on a given day
- Whether there is a fertility concern
Ovulation predictor tests, basal body temperature tracking, and cervical mucus observations provide different information. None of them is perfect on its own. Calendar estimates are not a reliable method of contraception.
Questions about ovulation
Can this calculator tell me exactly when I ovulate?
No. It estimates a likely date using cycle length. Ovulation timing can shift, and the calculator cannot confirm that it occurred. If knowing the exact timing matters for your care, ask a healthcare professional which tracking method is appropriate.
How long is the fertile window?
The calculator shows a seven-day window: five days before the estimated ovulation day, the day itself, and the day after. This reflects general patterns of sperm and egg survival, but it is not a guarantee for any individual cycle.
Does ovulation always happen on day 14?
No. Day 14 is a common example for a 28-day cycle, but the timing is relative to the next period, not a fixed day of the cycle. Shorter or longer cycles shift the estimate.
General references
These organizations provide general health information. They are external sites with their own content and policies, and this site is not affiliated with them.