Ovulation Calculator with Calendar

Ovulation Calculator

This ovulation calculator helps you estimate the days you're most likely to be fertile based on the first day of your last period and the average length of your menstrual cycle. Knowing your fertile window can assist in planning or preventing pregnancy.

Please enter a valid date.
Please enter a valid number of days (21-35).
Estimated ovulation day
Fertile window
  • If you have irregular menstrual periods, it’s important to consult a healthcare professional to determine the underlying cause and receive appropriate treatment.