Project cycle dates from the first day of the last menstrual period, average cycle length, and luteal-phase estimate.
Calculate with the Ovulation Calculator
Enter the details below. Your values stay in this browser and are validated before results are shown.
Ovulation Calculator results
How to use the Ovulation Calculator
- Select the requested method and unit system where available.
- Enter measured values carefully using the labels and active units.
- Select Calculate or press Enter.
- Read the estimate together with its method, assumptions, limitations, and safety notice.
Worked example
With a 28-day cycle and 14-day luteal phase, ovulation is estimated around 14 days before the next period.
Interpreting the estimate
Ovulation can vary between and within cycles. Pregnancy can occur outside the displayed estimate.
Limitations
- Irregular cycles, postpartum changes, breastfeeding, perimenopause, medication, illness, and health conditions may reduce accuracy.
- This calculator cannot confirm ovulation.
Frequently asked questions
Is the fertile window exact?
No. It is an estimate based on average cycle timing, and actual ovulation can occur earlier or later.
Is the ovulation calculator a medical assessment?
No. It provides an educational estimate from the values entered and cannot account for every individual or clinical factor.
Does CalculatorCheck store my health information?
No. The calculation runs in your browser, and the entered values are not sent to a server or added to the page URL.