Ovulation Calculator
Track ovulation day and fertile window for conception planning
Estimated Ovulation Day
How to Use
- Enter the first day of your last menstrual period.
- Enter your typical menstrual cycle length (21–35 days; default 28).
- Click 'Calculate' to see your ovulation date and fertile window.
- The fertile window includes the 5 days before ovulation, ovulation day, and 1 day after.
- View the 3-month calendar to plan ahead for multiple cycles.
About Ovulation
How Ovulation Works
Ovulation occurs when a mature egg is released from the ovary. This typically happens around day 14 of a 28-day cycle, but varies with cycle length. The formula is: Ovulation Day = First Day of Last Period + (Cycle Length − 14). The 14 days after ovulation (luteal phase) is relatively consistent across women, regardless of cycle length.
Fertile Window
Sperm can survive in the female reproductive tract for up to 5 days, while an egg remains viable for only 12–24 hours after ovulation. This creates a fertile window of about 6 days: the 5 days before ovulation plus the day of ovulation itself. The highest chance of conception is 1–2 days before ovulation.
Signs of Ovulation
Physical signs of ovulation include: changes in cervical mucus (becomes clear and stretchy, like raw egg white), a slight rise in basal body temperature (0.2–0.5°C), mild one-sided pelvic pain (mittelschmerz), breast tenderness, and increased libido. Ovulation predictor kits (OPKs) detect the LH surge that occurs 24–36 hours before ovulation.
Cycle Variation
A normal menstrual cycle ranges from 21–35 days. Cycles shorter than 21 or longer than 35 days may indicate hormonal imbalances. Stress, illness, significant weight changes, and travel can temporarily disrupt cycle regularity. Women with irregular cycles benefit most from tracking multiple cycles or using OPKs to confirm ovulation timing.
Key Features
- Calculates ovulation day based on cycle length
- Shows the full 7-day fertile window
- Displays next period expected date
- 3-month calendar view for planning ahead