🌸 Ovulation Calculator
Estimate your most likely ovulation day, fertile window, and next expected period based on the first day of your last period and your average cycle length.
How ovulation is estimated
Ovulation typically occurs about 12-16 days before the start of your next period, driven by the length of the luteal phase (the time between ovulation and your next period), which is generally more consistent than the first half of the cycle.
How this calculator works
Enter the first day of your last period, your average total cycle length, and your typical luteal phase length (14 days is average). The calculator subtracts the luteal phase from your cycle length to estimate your ovulation day, then shows a fertile window spanning roughly 5 days before ovulation through 1 day after, since sperm can survive several days while the egg is viable for about 24 hours. It also estimates your next expected period.
These are statistical estimates based on average cycle patterns; actual ovulation timing varies from cycle to cycle and can be affected by stress, illness, and other factors. This tool is for general educational and family planning purposes only and is not a substitute for professional medical advice or clinical fertility tracking.