Ovulation Calculator
Estimate ovulation, the likely fertile window, and future cycle dates using your last period and cycle pattern.
Your cycle details
Enter 2–12 lengths separated by commas, for example: 27, 29, 28.
If unknown, 14 days is a common planning assumption.
Your estimate
Estimated ovulation date
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How this ovulation estimate works
The calculator estimates the next period from the selected cycle length, then counts backward by the luteal-phase estimate to approximate ovulation. The displayed fertile window runs from five days before through one day after the estimated ovulation date.
Understanding fertile timing
Ovulation often happens about 10–16 days before the next period, not always on cycle day 14. Tracking cervical mucus, basal body temperature, or ovulation-test results may provide additional information, but each has limitations.
Frequently asked questions
Can this calculator confirm ovulation?
No. It predicts dates from cycle information and cannot verify whether or when ovulation occurred.
Can I use this for contraception?
No. Do not rely on a calendar estimate alone to prevent pregnancy. Discuss reliable contraceptive choices with a qualified healthcare professional.
What if my cycles are irregular?
The forecast becomes less reliable as cycle variation increases. Consider clinical advice if cycles are persistently irregular or you have fertility concerns.
When should I seek fertility advice?
Timing depends on age, medical history, and local guidance. A healthcare professional can advise when an assessment is appropriate.
Medical notice
This calculator is educational and does not diagnose ovulation, fertility, pregnancy, or reproductive conditions. Seek medical advice for severe pain, heavy bleeding, missed periods, or other concerns.
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