Ovulation Calculator — Find Your Fertile Window
Estimate your ovulation date and fertile window based on your last menstrual period and average cycle length. Most women ovulate 14 days before their next expected period.
How to use it
- Enter the first day of your last menstrual period.
- Enter your average cycle length in days (typically 21–35 days; 28 is average).
- Read your estimated ovulation date, fertile window, and expected next period.
What Is the Fertile Window?
The fertile window spans the 5 days before ovulation and the day of ovulation itself — 6 days total. Sperm can survive in the reproductive tract for up to 5 days.
Signs of Ovulation
Common signs include a slight rise in basal body temperature, changes in cervical mucus (clear and stretchy like egg whites), mild pelvic pain, and a positive ovulation predictor kit (OPK) test.
The formula
Frequently asked questions
When do I ovulate?
Most women ovulate approximately 14 days before their next period. For a 28-day cycle, that is around day 14.
How long is the fertile window?
Approximately 6 days: the 5 days before ovulation and the day of ovulation itself.
Can I get pregnant right after my period?
It is unlikely but possible, especially with shorter cycles. Sperm can survive up to 5 days.
How accurate is this calculator?
This is an estimate based on average cycle patterns. Actual ovulation varies. Use basal body temperature charting or OPKs for precise tracking.