When does ovulation happen?
For most people ovulation falls about 14 days before the next period — not 14 days after the last one, which is a common mix-up. That distinction matters most if your cycle is longer or shorter than the textbook 28 days. This calculator counts back from your estimated next period to place ovulation.
Your fertile window
You are most likely to conceive in the days leading up to and including ovulation. Because sperm can survive a few days inside the body, the fertile window is usually counted as roughly the five days before ovulation plus ovulation day itself — about six days in total.
Signs that line up with the dates
Many people notice physical signs around ovulation: a slight rise in body temperature, changes in cervical mucus, or a mild twinge on one side. Tracking these alongside the estimated dates gives a fuller picture than dates alone.
An important note
These are estimates based on averages and a regular cycle, provided for general information. They are not medical advice and not a reliable method of contraception. If you are trying to conceive and it is taking time, or your cycles are irregular, a doctor or fertility specialist can help.
Frequently asked questions
How many days am I fertile?
Roughly six: the five days before ovulation and ovulation day. Chances are highest in the two days just before.
Can I rely on this to prevent pregnancy?
No. Use a proper contraceptive method; this estimate is not safe for that purpose.
Is this calculator free?
Yes — free, no signup, and your dates are never stored.