About the Ovulation Calculator
Predict your most fertile days. Enter the first day of your last period and your usual cycle length to see your estimated ovulation date, fertile window and the next three cycles.
Key features
- Estimated ovulation date
- Fertile window and most fertile days
- Next period and pregnancy test date
- Next three cycles
- Cycles from 21 to 45 days
- Adjustable luteal phase
Find your most fertile days
If you're trying to conceive, timing matters. Enter the first day of your last period and your usual cycle length to estimate your ovulation date and fertile window for the next three cycles.
Ovulation by cycle length
| Cycle length | Approximate ovulation day |
|---|---|
| 24 days | Day 10 |
| 28 days | Day 14 |
| 30 days | Day 16 |
| 32 days | Day 18 |
| 35 days | Day 21 |
Signs of ovulation
- Clear, stretchy cervical mucus (like raw egg white)
- A small rise in basal body temperature after ovulation
- Mild one-sided pelvic pain for some women
- A positive ovulation (LH) test 24–36 hours before ovulation
See a doctor if you've been trying to conceive for 12 months (6 months if you're 35 or older), or if your cycles are very irregular.
Related calculators
Period calculator, pregnancy due date calculator, and BMI calculator.
How to use the Ovulation Calculator
- Enter your numbers in the fields above. Units and options can be changed at any time.
- The result updates instantly as you type; there's no calculate button to press.
- Check the breakdown under the main result for the details behind the number.
- Adjust the inputs to compare scenarios, for example a different rate or term.