Fertile days calculator
See the days you are most likely to conceive over your next three cycles.
Enter your details to see your result.
What the numbers mean
| Date | How it is worked out |
|---|---|
| Next period | First day of your last period + your cycle length |
| Ovulation | About 14 days before your next period |
| Fertile days | The 5 days before ovulation, the day of ovulation and the day after |
Sperm can live for up to about 5 days, so the days before ovulation count. If your cycles vary from month to month, these dates are less reliable.
When to see a doctor
- You have been trying for a year without success, or for 6 months if you are over 35.
- Your periods are irregular, very painful or very heavy, or have stopped.
- You have a condition such as PCOS or thyroid disease and are planning a pregnancy.
Talk to a doctor
Bring your numbers to your visit. Our doctors will explain what they mean for you and what to do next.
This tool is a guide, not a diagnosis; your doctor’s advice comes first. Nothing you type leaves your device.