🔗 Use full-page Period Calculator here for best experience

Calculate My Cycle

How to Use the Period Calculator

  1. Enter the first day of your last period — this is Day 1 of your cycle
  2. Enter your average cycle length — most women have a 21–35 day cycle (average: 28)
  3. Enter your period duration — how many days your period typically lasts
  4. Click Calculate — instantly see your next period, ovulation date, fertile window, and 6-cycle forecast

Understanding Your Menstrual Cycle

A menstrual cycle is counted from Day 1 of your period to Day 1 of the next period. The average is 28 days, but anything between 21 and 35 days is considered normal.