Ovulation Calculator

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

First Day of Last Period

Average Cycle Length

days

Typical cycles are 21-35 days. Average is 28 days.

Period Length

days

How many days does your period usually last?

Coursera Plus

Unlimited access to 7,000+ world-class courses, hands-on projects, and job-ready certificate programs.

Start Learning

Fertile Window

Enter dates

Your estimated fertile window based on a 28-day cycle

Ovulation

Ovulation Date

-

Next Period

Expected Date

-

Phase

Current Phase

Follicular Phase

Cycle Overview

Menstrual Phase

Days 1-5

Follicular Phase

Days 6-13

Ovulation (Fertile Window)

Days 9-15

Luteal Phase

Days 16-28

Documentation

How Ovulation Tracking Works

Ovulation typically occurs about 14 days before your next period starts. The fertile window spans approximately 6 days: the 5 days before ovulation and the day of ovulation itself.

Important

This calculator provides estimates based on average cycle patterns. For accurate tracking, consider using additional methods like basal body temperature or ovulation predictor kits.

The Calculation

Ovulation Day = Cycle Length − 14

Day 14 = 28 − 14

The luteal phase (after ovulation) is typically 14 days for most women, which is why we subtract 14 from your cycle length to estimate ovulation day.

Last Updated: February 2026

Disclaimer: This calculator is for informational purposes only and should not be used as a contraceptive method or for medical diagnosis. Consult a healthcare provider for personalized fertility advice.