Health & Fitness
Ovulation Calculator
Estimate your ovulation day and fertile window from your last period and cycle length — plus when your next period is due — to help you plan or track conception.
days
Estimated ovulation
June 15, 2026
🌸 Fertile windowJun 10 – Jun 16, 2026
📅 Next periodJune 29, 2026
How to use the ovulation calculator
Enter the first day of your last period and your average cycle length. The calculator estimates the day you are most likely to ovulate, your fertile window of around six days, and the date your next period is due. For trying to conceive, the days just before ovulation are the most fertile.
How ovulation is estimated
ovulation = last period + (cycle length − 14)
fertile window = ovulation − 5 days to ovulation + 1 day
Ovulation typically occurs about 14 days before the next period, so the day depends on your cycle length, not just the calendar. Because sperm can survive up to five days, the window opens several days before ovulation and closes about a day after.
Frequently asked questions
For an average cycle, ovulation happens about 14 days before your next period starts — so roughly day 14 of a 28-day cycle. The calculator works it out from your last period and your cycle length, since ovulation timing shifts with cycle length.