Ovulation Calculator

Enter your dates and assumptions, then select Calculate.

Ovulation and Fertile Window Calculator

Cycle detailsFirst day of last periodAverage cycle lengthdaysExpected cycle variation+/- daysLuteal-phase estimatedays

Timing and projection assumptions

Fertile days before ovulationdaysFertile days after ovulationdaysPregnancy test after ovulationdaysPregnancy duration from ovulationdaysCycles to projectcycles

Example values are prefilled for demonstration. Review and replace every value with your own cycle information.

Important: This is an educational calendar estimate. Ovulation can vary even when cycles seem regular. Do not use it to confirm ovulation, diagnose a condition, or as birth control.