Ovulation Calculator
Find your fertile window, ovulation day, and next period date based on your cycle length and last period.
Ovulation Calculator
Enter your last period date and average cycle length to find your fertile window, estimated ovulation day, and next period.
Your Cycle Overview
Calendar View
Period
Fertile window
Ovulation day
Note: This calculator estimates dates based on average cycle patterns. Actual ovulation can vary by several days. For family planning purposes, consult a healthcare provider.
How Ovulation Calculation Works
Ovulation typically occurs about 14 days before your next period (the luteal phase). To find your ovulation day, subtract your luteal phase length from your total cycle length. Your fertile window spans the 5 days before ovulation plus the ovulation day itself — the period when conception is most likely.
Cycle Phases
- Menstruation (Days 1–5): Period bleeding; Day 1 is the first day of your period.
- Follicular phase (Days 1–13): Estrogen rises; follicles develop in the ovaries.
- Ovulation (around Day 14): LH surge triggers egg release. This is the peak fertility day.
- Luteal phase (Days 15–28): Progesterone rises; uterine lining thickens. If no fertilization, period begins.