Ovulation calculator
You usually ovulate about 14 days before your next period. Your most fertile days are the 5 days before ovulation and the day itself, especially the 2 days before. Enter your last period and cycle length to see your dates.
How the ovulation calculator works
The second half of the menstrual cycle, from ovulation to your next period, is fairly constant at about 14 days. The first half varies from woman to woman. So the calculator takes your cycle length, counts back 14 days from your next expected period to estimate ovulation, and marks the 5 days before it as your fertile window.
| Cycle length | Likely ovulation | Most fertile days |
|---|---|---|
| 24 days | Day 10 | Days 8 to 10 |
| 26 days | Day 12 | Days 10 to 12 |
| 28 days | Day 14 | Days 12 to 14 |
| 30 days | Day 16 | Days 14 to 16 |
| 32 days | Day 18 | Days 16 to 18 |
| 35 days | Day 21 | Days 19 to 21 |
Day 1 is the first day of your period.
Signs that you are ovulating
- Cervical mucus becomes clear, slippery and stretchy, like raw egg white.
- A positive ovulation test shows the LH hormone surge, usually 24 to 36 hours before ovulation.
- Your temperature rises slightly, by about 0.2 to 0.5 °C, after ovulation.
- Some women feel a twinge of pain on one side of the lower tummy, or notice a higher sex drive.
Tips if you are trying to conceive
Have sex every 2 to 3 days throughout your cycle, so there are always sperm waiting when you ovulate. Take 400 micrograms of folic acid daily from at least 3 months before you try. Most couples conceive within a year; see a doctor after a year of trying, or after 6 months if you are 35 or older. Read our 10 tips for getting pregnant.
Ovulation questions
When do I ovulate?
Most women ovulate about 14 days before their next period starts. In a 28-day cycle that is around day 14, but in a 32-day cycle it is around day 18, and in a 25-day cycle around day 11. Count back 14 days from when your next period is due.
What is the fertile window?
The fertile window is the 6 days ending on the day of ovulation: the 5 days before and the day itself. Sperm can live for up to 5 days, while the egg survives about 12 to 24 hours. The best chance of pregnancy comes from sex in the 2 days before ovulation.
How accurate is an ovulation calculator?
It is a good starting point if your cycles are regular, but ovulation can shift by a few days from month to month. Ovulation predictor kits, which detect a hormone surge in your urine, and tracking cervical mucus or temperature can help confirm when you ovulate.
Can I use an ovulation calculator with irregular periods?
It is less reliable. If your cycles vary a lot, have sex every 2 to 3 days throughout the month, and use ovulation tests. See a doctor if your cycles are often shorter than 21 or longer than 35 days, as this can be a sign of conditions such as PCOS.
Can I use this to avoid pregnancy?
No. Calendar calculations are not a reliable method of contraception. Talk to a doctor about contraception options.