Free tool

Understand your fertile window with confidence

Estimate your fertile window, predicted ovulation day and current menstrual cycle phase based on your last menstrual period and average cycle length. Learn more about your reproductive health and plan naturally with greater confidence.

Ovulation Calculator

Based on menstrual cycle length

First day of your last menstrual period (LMP)Average cycle length28 days

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This calculator works best for women with relatively regular menstrual cycles.

Enter your last menstrual period and cycle length to view your estimated ovulation day, fertile window, current cycle phase, days until ovulation, next expected period, personalised cycle calendar and a shareable fertility summary.

Menstrual

Follicular

Ovulation

Luteal

Your menstrual cycle timeline

Enter your details to estimate your fertile window, ovulation day and current cycle phase.

Fertility tip: Sperm can survive in the female reproductive tract for up to five days, while the egg is generally viable for 12–24 hours after ovulation. This is why the fertile window begins several days before ovulation.