Period & Ovulation Calculator
Enter your last period start and typical cycle and period length — we estimate upcoming periods, ovulation, and a fertile window. For comprehensive tracking, apps like Flo or Clue offer more features.
Inputs
Cycle calendar
Color-coded calendar for the selected cycle
Rough due date (this cycle’s ovulation)
Menstrual cycle basics
A typical cycle includes menstrual, follicular, ovulatory, and luteal phases. Ovulation often occurs about 14 days before the next expected period — not always “day 14 of the cycle” unless your cycle is very regular and 28 days. Signs such as basal body temperature shift, cervical mucus changes, or LH test surges can help time ovulation better than a calendar alone.
Irregular cycles (large variation in length), very heavy bleeding, severe pain, or missed periods warrant medical evaluation — do not rely on this page for diagnosis.
If you conceive around ovulation, a rough due date from LMP is on the order of 280 days — use our Pregnancy Due Date calculator for Naegele-style estimates and discuss dating scans with your clinician.