Ovulation Calculator

Enter your last period start date and cycle length, and the calculator subtracts a fixed 14-day luteal phase to estimate ovulation at cycle length minus 14. For a 28-day cycle, that is day 14. It marks the five days before ovulation, ovulation day, and the following day. That inclusive range contains seven calendar dates.

If your cycles are regular, the predicted window is a reasonable starting point, but the fixed 14-day luteal phase is an average and your real luteal phase may differ. Stress, illness, travel, and hormonal changes can shift actual ovulation by several days. Treat the output as an estimate, not a diagnosis. For fertility concerns or trouble conceiving, talk to a clinician.

Most adults have cycles between 21 and 35 days, with 28 days being the classic textbook number. The calculator accepts any cycle from 20 to 45 days. A few days of variation between cycles is normal; persistent irregularity outside that range is worth discussing with a doctor.

See a doctor if your cycles are shorter than 21 days or longer than 35 days, vary by more than 7 to 9 days between cycles, or you have been trying to conceive for 12 months (or 6 months if you are over 35). Abnormal bleeding or sudden changes in cycle pattern are also worth raising promptly.

No. Ovulation day is one estimated date. Sperm may survive for several days, while an egg remains viable for a much shorter period. This calculator marks five days before the estimate through one day after it, which is seven calendar dates inclusive. Actual ovulation can shift, so do not use this range as contraception or as proof that ovulation occurred.