Period Tracker Online – Next Period, Ovulation and Fertile Window
Period Tracker
Calculate your next period date, identify your fertile window, and estimate your ovulation day accurately and privately.
Quick answer
A period tracker online predicts when your next period will start and when you are most likely to ovulate. Enter the first day of your last period, your average cycle length and how many days your period usually lasts, then click Calculate Cycle. You will see your expected next period date, estimated ovulation day and your fertile window.
Our free period tracker online works without an app or account, and nothing you enter leaves your browser. It is a quick way to plan for your next period, holidays or events, or to understand which days in your cycle are most fertile.
Predictions are based on averages. Cycles can change with stress, illness, travel, breastfeeding, hormonal contraception and conditions such as PCOS. This period tracker online is not a form of birth control and should not be used to prevent pregnancy.
How the Period Tracker Works
- Next period: first day of last period + your cycle length.
- Ovulation: about 14 days before the next period starts.
- Fertile window: the 5 days before ovulation plus ovulation day, because sperm can survive up to about 5 days.
Example: if your last period began on 20 September 2026 and your cycle is 28 days, your next period is expected on 18 October 2026, ovulation around 4 October and your fertile window from 30 September to 5 October.
What Is a Normal Cycle?
| Measure | Typical range |
|---|---|
| Cycle length | 21 to 35 days in adults |
| Period duration | 2 to 7 days |
| Ovulation | About 12 to 16 days before the next period |
| Variation month to month | Up to about 7 to 9 days can be normal |
How to Use the Period Tracker
Here is how to use the period tracker online.
Step 1: Enter the First Day of Your Last Period
Pick the date your last period started in the calendar. Count the first day of full bleeding, not spotting.
Step 2: Set Your Cycle Length and Period Duration
Choose your average cycle length (21 to 35 days) and how long your period usually lasts. Use 28 and 5 days if you are unsure.
Step 3: See Your Expected Next Period Date
Click Calculate Cycle. The top card shows the date your next period should start and how many days away it is.
Step 4: Check Your Ovulation Day and Fertile Window
Below the next period date you will see your estimated ovulation day and the fertile window when pregnancy is most likely.
Tips for More Accurate Predictions
- Track at least three cycles and use your average length.
- Write down the start date each month in a note or calendar.
- If your cycles vary a lot, treat the predicted date as a range of a few days.
- Signs like stretchy cervical mucus or a positive ovulation test can confirm ovulation.
When to See a Doctor
- Your periods are regularly shorter than 21 days or longer than 35 days.
- A period lasts longer than 7 days or bleeding is very heavy.
- Periods stop for more than 90 days and you are not pregnant.
- You have severe pain, bleeding between periods or after sex.
Why Use a Period Tracker Online?
Many tracking apps ask for an account and store sensitive health data. A period tracker online that runs in your browser gives the same core predictions in seconds while keeping your information on your device. It is also handy for checking dates on a shared or work computer without installing anything.
Period Tracker Online vs Tracking Apps
A period tracker online is best for fast, private predictions. You enter one date, get your results and close the page, with nothing saved to a server or shared with advertisers.
Tracking apps are useful if you want long-term charts and reminders. Many people use both: an app for daily logging and this period tracker online to double-check dates or to help a friend or partner understand the cycle.
- No download, login or email needed for this period tracker online.
- Works on Android, iPhone, tablets and computers.
- Free to use as often as you like.
Frequently Asked Questions
Is this period tracker online free?
Yes. It is free, needs no account and keeps your data in your browser.
How is my next period predicted?
It adds your average cycle length to the first day of your last period.
When do I ovulate?
Ovulation usually happens about 14 days before your next period starts.
What is the fertile window?
The 5 days before ovulation and the day of ovulation, when pregnancy is most likely.
Can I use this to avoid pregnancy?
No. Predictions are estimates and should not be used as birth control.
Why is my period late?
Stress, illness, travel, weight change, breastfeeding or pregnancy can delay a period. Take a test or speak to a doctor if you are concerned.