Ovulation Calculator

Enter the first day of full flow of your most recent period as the last menstrual period (LMP). Set average cycle length to the typical number of days from one period start to the next—after logging several months if you can.

Leave luteal phase at 14 unless you have charting data suggesting a different stable length (often 12–16 days). Shorter or longer luteal phases move the estimated ovulation date forward or backward even when cycle length stays the same.

The next period is placed at LMP + cycle length. Ovulation is placed cycle length − luteal phase days after LMP—equivalent to “luteal days before the next period.” The fertile window listed here runs from five days before that ovulation date through ovulation day, a common convention; it does not include the day after ovulation.

The fertile window spans about six days — the five days before ovulation plus the day of ovulation itself. Sperm can survive in the reproductive tract for up to several days, while the egg is viable for roughly 12–24 hours after release. The highest probability of conception is often in the two to three days leading up to and including ovulation day.

Common ovulation signs include a slight rise in basal body temperature (about 0.5–1°F after ovulation), cervical mucus that becomes clear and stretchy (like egg whites), mild one-sided pelvic discomfort (mittelschmerz), breast tenderness, and libido changes. Combining calendar estimates with these cues improves timing.

No. Irregular cycles, pain, very heavy bleeding, or difficulty conceiving deserve evaluation by a clinician or midwife. Use this page for education and rough planning only.