Ovulation Calculator
Estimate your ovulation date, fertile window, and next expected period based on the first day of your last period and your usual cycle length.
Typical cycles range from 21 to 45 days.
Estimated Ovulation
Mon, Apr 20, 2026
Fertile Window
Apr 15 to Apr 20
Next Expected Period
Mon, May 4, 2026
Cycle Length Used
28 days
April 2026
Next 3 Predicted Cycles
Cycle starting Mon, May 4, 2026
Next period: Jun 1Estimated ovulation
Mon, May 18, 2026
Fertile window
May 13 to May 18
Cycle starting Mon, Jun 1, 2026
Next period: Jun 29Estimated ovulation
Mon, Jun 15, 2026
Fertile window
Jun 10 to Jun 15
Cycle starting Mon, Jun 29, 2026
Next period: Jul 27Estimated ovulation
Mon, Jul 13, 2026
Fertile window
Jul 8 to Jul 13
How to Use
- Select the first day of your last menstrual period.
- Enter your average cycle length, usually between 21 and 45 days.
- Review your estimated ovulation date, fertile window, and next expected period.
- Use the calendar and 3-cycle forecast to plan ahead, then confirm with ovulation tests or your healthcare provider if needed.
Frequently Asked Questions
How is ovulation estimated?
Ovulation is often estimated to happen about 14 days before your next period. This calculator adjusts that estimate using your average cycle length, then highlights the days leading up to ovulation as your fertile window.
What is the fertile window?
The fertile window includes the five days before ovulation and the day of ovulation itself. Sperm can survive for several days, so pregnancy is most likely during this span.
Are ovulation calculator predictions exact?
No. Cycle length can vary from month to month, and ovulation may happen earlier or later than expected. Use this as a planning estimate, not a medical diagnosis or guarantee.
What if my periods are irregular?
If your cycles are irregular, predictions may be less accurate because the calculation depends on a typical cycle length. Tracking cervical mucus, basal body temperature, or ovulation tests may give you more reliable clues.