Ovulation Calculator
Find your most fertile days and likely ovulation date from your cycle.
Enter your last period date to estimate ovulation.
This tool is for general information only and is not medical advice. Talk to a qualified healthcare professional before making health decisions.
About the Ovulation Calculator
This ovulation calculator estimates when you are most likely to ovulate and your fertile window, using the first day of your last period and your average cycle length.
Ovulation typically happens about 14 days before your next period, and the fertile window covers the days leading up to and just after it. The tool also shows when your next period is expected.
These are estimates based on a regular cycle. For accuracy, combine with other signs or tests. Everything is calculated in your browser.
Key features
- Most likely ovulation day
- Fertile window range
- Next period estimate
- Adjusts for cycle length
How to use
- 1Enter the first day of your last period.
- 2Enter your average cycle length.
- 3Read your fertile window and ovulation day.
Frequently asked questions
- When am I most fertile?
- The fertile window is roughly the five days before ovulation plus the day of ovulation, with the highest chance in the two days before it.
- Does this work with irregular cycles?
- It assumes a fairly regular cycle. If your cycles vary a lot, the estimate is less reliable and ovulation tests may help.