Ovulation Calculator

Find your likely ovulation day and fertile window using the first day of your last period and your typical cycle length.

Format DD/MM/YY — slashes are added automatically.
Leave blank if your cycle is about 28 days.

Results

Estimated ovulation day
Fertile window
Next period estimate
Cycle day today

How this calculator works

This calculator estimates ovulation timing from your last menstrual period (LMP) and typical cycle length. It assumes ovulation occurs about 14 days before your next period, which can vary by person and cycle.