How to use the Ovulation Calculator tool
3 simple steps · under a minute
-
Enter your last period
Pick the first day of your most recent period.
-
Add your cycle length
Count from the first day of one period to the first day of the next. 28 days is average.
-
See your fertile days
Read your fertile window, ovulation date and a calendar for six cycles.
About Ovulation calculator
Ovulation is when an ovary releases an egg, usually about 14 days before your next period. Because sperm can survive for up to five days and the egg for about a day, your fertile window is the five days before ovulation plus the day of ovulation itself. This ovulation calculator finds those days for you.
Enter the first day of your last period and your average cycle length to see your fertile window, ovulation date and next period, plus a calendar for the next six cycles. If your cycles are irregular, ovulation tests or tracking basal body temperature give a more precise picture.
Fertile window
The six days each cycle when pregnancy is most likely.
Six-cycle calendar
Plan ahead with dates for your next six periods and ovulation days.
Your own cycle
Works with cycles from 20 to 45 days and your luteal phase length.
Frequently asked questions
When do I ovulate?
Usually about 14 days before your next period starts. In a 28-day cycle, that is around day 14; in a 32-day cycle, around day 18.
What is the fertile window?
The five days before ovulation and the day of ovulation — the six days each cycle when sex can lead to pregnancy.
What are the signs of ovulation?
Clear, stretchy cervical mucus, a slight rise in basal body temperature after ovulation, mild one-sided pelvic pain and a positive ovulation test.
Can I use this as birth control?
No. Cycle-based estimates are not reliable enough to prevent pregnancy.
Is this medical advice?
No. Speak to a doctor if you have irregular cycles or are having trouble conceiving.