Ovulation Calculator
Find your fertile window, ovulation day, next period, and when to take a pregnancy test, for this cycle and the next five.
Your cycle
From your last six or more cycles. Ovulation and period dates use the average.
More options
The luteal phase runs from ovulation to your next period. Leave it at 14 unless you have tracked yours.
Worked out in your browser; your dates are not stored. Not a method of birth control.
Ovulation around
- Most fertile days
- Next period
- Pregnancy test from
- Due date if you conceive this cycle
Enter the first day of your last period to see your fertile days.
- Period
- Fertile
- Most fertile
- Ovulation
- Today
Your next six cycles
| Period starts | Fertile window | Ovulation | Test from | Due date if pregnant |
|---|---|---|---|---|
Ovulation can move from cycle to cycle, so these are estimates, not medical advice. Ovulation tests or tracking your temperature show when it really happens.
About the Ovulation Calculator
The ovulation calculator estimates when you ovulate and which days you are most likely to get pregnant. Enter the first day of your last period and your cycle length to see your fertile window, ovulation day, next period, and when to take a pregnancy test for the next six cycles. If your cycles vary, enter your shortest and longest cycle instead.
How to use it
- 1 Enter the first day of your last period.
- 2 Enter your usual cycle length, or your shortest and longest cycles if they vary.
- 3 See your fertile window and ovulation day on the calendar.
- 4 Scroll the next six cycles, and copy the share link to keep them.
Frequently asked questions
When do I ovulate?
Ovulation usually happens about 14 days before your next period starts, not 14 days after the last one. With a 28-day cycle that is around day 14; with a 32-day cycle it is around day 18.
What is the fertile window?
It is the six days ending on ovulation day: the five days before and the day itself. Sperm can live up to five days, and an egg lives about a day, so these are the days sex can lead to pregnancy. The two days before ovulation and the day itself are the most fertile.
How does the calculator work with irregular periods?
Enter your shortest and longest cycles from the last six months or more. The fertile window then runs from the shortest cycle minus 18 days to the longest cycle minus 11 days. This calendar method is wider and less precise, so ovulation tests or tracking your temperature help.
When should I take a pregnancy test?
Home tests are most reliable from the first day of your missed period, about 14 days after ovulation. Some sensitive tests can show a result a few days earlier, but a negative result before your period is due may be wrong.
Can I use this calculator to avoid pregnancy?
No. Cycles and ovulation vary from month to month, so a calendar estimate is not reliable birth control. Talk to a doctor or nurse about contraception.
How accurate is an ovulation calculator?
It gives a good starting point if your cycles are regular, but it cannot detect ovulation. Ovulation predictor kits, cervical mucus changes, and basal body temperature show when it actually happens.