Everything is worked out in your browser and saved on this device for next time.
About the ovulation calculator
Ovulation is the day an egg is released. You can get pregnant on the six days that end on that day: the five days before ovulation and the day of ovulation. This is called the fertile window. The two days right before ovulation are usually the most fertile.
Type the first day of your last period and your cycle length. The calculator shows your likely ovulation day, the fertile window, the most fertile days, the day your next period is expected, and the day to take a pregnancy test. A table below shows the next cycles.
It is a calendar method: it works best if your cycle is regular. It is not birth control.
How to use it
- Pick the first day of last period
- Type your cycle length (days) — from the first day of one period to the first day of the next — or press a button
- Read the likely ovulation day and the fertile window
- Open More options to change the luteal phase or to show 3, 6 or 12 cycles
How the days are worked out
Ovulation happens about 14 days before the next period. So:
ovulation day = first day of the period + cycle length − 14
| Cycle length | Ovulation day | Fertile window (cycle days) | Next period |
|---|---|---|---|
| 24 days | day 10 | day 5 – day 11 | day 25 |
| 26 days | day 12 | day 7 – day 13 | day 27 |
| 28 days | day 14 | day 9 – day 15 | day 29 |
| 30 days | day 16 | day 11 – day 17 | day 31 |
| 32 days | day 18 | day 13 – day 19 | day 33 |
| 35 days | day 21 | day 16 – day 22 | day 36 |
Day 1 is the first day of the period.
Why the luteal phase matters
The time between ovulation and your next period is the luteal phase. It is about 14 days for most women, but can be 10 to 16 days. If you know yours, type it under More options and the dates move.
Signs of ovulation
- Clear, stretchy cervical mucus, like raw egg white
- A small rise in body temperature after ovulation
- A positive ovulation test (LH test)
- Mild pain on one side of the belly in some women
Use the calendar together with these signs for a better guess.
Frequently asked questions
When do I ovulate?
About 14 days before your next period. With a 28-day cycle that is day 14.
What are the best days to get pregnant?
The two days before ovulation and the day of ovulation. Sex every day or every second day during the fertile window gives a good chance.
Can I get pregnant outside the window?
Very rarely if your cycle is regular. If your cycle varies a lot, the window can move.
My cycle is irregular. Does this work?
Only roughly. Use the shortest and the longest cycle you had and compare, and add ovulation tests. A doctor can help.
Can I use this as birth control?
No. Sperm can live up to five days, and ovulation can come early. This calculator is not a way to prevent pregnancy.
Is this medical advice?
No. It is a general guide. Ask a doctor if you have trouble getting pregnant.
Good to know
- Your date is saved only in this browser
- Nothing you type is sent anywhere
- Dates are shown in your language and your local format
Related tools
- Pregnancy Due Date Calculator — when the baby is due
- Date Calculator — add or subtract days from a date
- Age Calculator — exact age
- Countdown to Date — count the days
- Sleep Calculator — sleep better
