Ovulation Calculator
Fertile window and ovulation for the next cycles.
Enter the first day of your last period to estimate your fertile window.
Estimates ovulation as roughly 14 days before your next period, with a 6-day fertile window. Cycles vary — this is an estimate for planning, not contraception or medical advice.
How to use the Ovulation Calculator
- 1 Enter the first day of your last period.
- 2 Set your average cycle length.
- 3 See your estimated ovulation date and fertile window for the next three cycles.
Examples
- ▸ With a 28-day cycle, ovulation is around day 14 and the fertile window spans roughly days 9–15.
Frequently asked questions
How is ovulation estimated?
Ovulation is estimated as about 14 days before your next expected period (cycle length − 14). The fertile window covers the 5 days before ovulation plus the day after.
Can I use this for birth control?
No. Cycles and ovulation vary month to month, so this is for conception planning and awareness only — not a contraception method.