Ovulation Calculator
Predict your ovulation day and most fertile days for the next three cycles based on your last period and cycle length.
About the Ovulation Calculator
The ovulation calculator predicts the day you are most likely to release an egg and the fertile window around it. If you are trying to conceive, these are the days when intercourse is most likely to lead to pregnancy. The calculator shows the next three cycles.
How to Use the Ovulation Calculator
- Enter the first day of your last period.
- Enter your average cycle length (28 days is typical).
- Press Calculate to see your fertile window and next periods.
Formula and How It Works
Ovulation usually happens about 14 days before the next period starts: ovulation day = last period + cycle length − 14. The fertile window covers the 5 days before ovulation and the day after, because sperm can live up to five days.
Frequently Asked Questions
Can I use this as birth control?
No. Cycles vary from month to month, so calendar methods are not reliable contraception.
What if my cycles are irregular?
Predictions will be less accurate. Ovulation test kits or tracking basal body temperature give a better picture.
Results are estimates for general information and are not medical or veterinary advice. Please speak to a qualified professional about your own situation.