MathIsimple
Health

Period Calculator

Track and predict your menstrual cycle, ovulation, and fertile window

100% FreeStep-by-Step Solutions
This calculator is for educational purposes only. Consult with a healthcare provider for medical advice.
Period Calculator
Enter your last period date and cycle information

Typically 21-35 days

Typically 2-7 days

Try These Examples
Click on any example to automatically fill the calculator
Example 1

28-day cycle, 5-day period

cycleLength: 28
periodLength: 5
Menstrual Cycle Basics

The menstrual cycle typically lasts 21-35 days, with the average being 28 days.

  • Menstruation: Days 1-5 (bleeding)
  • Follicular Phase: Days 1-13
  • Ovulation: Around day 14
  • Luteal Phase: Days 15-28
Fertile Window

The fertile window is the time when pregnancy is most likely to occur:

  • 5 days before ovulation
  • Day of ovulation
  • 1 day after ovulation

Sperm can survive up to 5 days in the reproductive tract.