Ovulation Calculator
Predict your ovulation day, fertile window, and next period for the next 6 cycles.
Cycle Details
Typical range is 21–35 days; the average is 28.
Enter your last period start date and a cycle length between 21–45 days.
Understanding Your Cycle
A menstrual cycle is split into four phases — menstrual, follicular, ovulation, and luteal. The follicular and luteal phases together usually total your full cycle length, while ovulation is anchored about 14 days before the next period starts.
Frequently Asked Questions
For most women the luteal phase is roughly 14 days. The calculator predicts ovulation by subtracting 14 days from your expected next-period date (last period + average cycle length).
It is the span of days when conception is possible — typically the 5 days before ovulation plus ovulation day itself, because sperm can survive in the reproductive tract for up to 5 days.
No. Cycle-based predictions are estimates only. Ovulation can shift due to stress, illness, or hormonal changes. Do not rely on this tool as a contraceptive method — consult a medical professional.
Enter your typical cycle length in days (the gap between the first day of one period and the first day of the next). The most common range is 21–35 days; 28 days is the population average.
Because ovulation is anchored 14 days before the next period — not 14 days after the previous period. A longer cycle pushes the next period back, which pushes ovulation back as well.