Ovulation and Period Calculator
Estimate your next period, fertile window and ovulation dates for three cycles using your last period and usual cycle length.
Most cycles are 21 to 35 days
Next period
Fertile window
Best chance of pregnancy
Likely ovulation
About 14 days before your next period
Your next three cycles
| Fertile window | Likely ovulation | Next period starts |
|---|
Trying to conceive?
Having sex every 1 to 2 days during your fertile window gives the best chance, because sperm can live up to 5 days and the egg survives about 24 hours after ovulation.
When to see a doctor
If your cycles are often shorter than 21 or longer than 35 days, your periods are very heavy or painful, or you’ve been trying for a year (6 months if you’re over 35) without success.
These dates are estimates based on an average cycle. Ovulation can shift from month to month, especially with irregular cycles, so this calculator should not be used as birth control. For general information only, not medical advice.
About this tool
The estimate assumes ovulation about 14 days before the next period. Real cycles vary, and predicted periods are not confirmation that a period occurred. Do not use these dates as contraception.