Find your most fertile days each cycle. Know exactly when to try — and when to start testing.
Enter your cycle details below
Enter your cycle information to see your personalized fertile window, ovulation date, and best days to conceive.
Your fertile window is the roughly six-day span each cycle when pregnancy is possible — the five days before ovulation and the day of ovulation itself. This is because sperm can survive in the reproductive tract for up to five days, while an egg is viable for only 12–24 hours after release.
Ovulation typically occurs 14 days before your next period starts (the luteal phase). So if your cycle is 28 days, you likely ovulate around day 14. A 32-day cycle means ovulation around day 18. We count backward from your expected next period to find ovulation day, then mark the five days prior as your fertile window.
Research shows your two most fertile days are:
Having sex every 1–2 days during your fertile window gives you the best chance. Daily intercourse is fine — it doesn't lower sperm quality in most men.
This calculator assumes a consistent luteal phase of 14 days, which is true for most women. However, the actual day of ovulation can vary by a few days even with regular cycles. For the most precise tracking, consider combining this calculator with:
If your cycles vary by more than 7 days, predicting ovulation by calendar alone is unreliable. OPK strips are especially helpful in this case. If your cycles are consistently shorter than 21 days or longer than 40 days, talk to your doctor — this could indicate a hormonal imbalance worth investigating.