Period Tracker
Predict your next period, fertile window and cycle day.
Next 3 predicted periods
Predictions are estimates based on a regular cycle and your saved data (kept privately in this browser). Cycles naturally vary; this tool does not prevent or confirm pregnancy and is not a substitute for medical advice.
About Period Tracker
Period Tracker is a free online tool that lets you predict your next period, fertile window and cycle day — straight from your browser, with no software to install, no sign-up, and no watermarks. It runs on Windows, Mac, Linux, Android, and iOS, so you can use it on whatever device you happen to have to hand.
Enter your figures and Period Tracker applies the right formula instantly, showing a clear breakdown so you understand how the result is reached — not just the final number. Adjust any input to compare scenarios side by side. Files and data are processed securely and removed automatically afterwards, and many steps run entirely on your own device for extra privacy. Because Period Tracker is completely free and unlimited, you can use it as often as you need for work, study, or personal projects.
Benefits of Period Tracker
Frequently asked questions
How does Period Tracker work out the result?
Enter your values and Period Tracker applies the relevant formula instantly, showing a clear breakdown alongside the final figure.
Can I compare different scenarios?
Yes — change any input and the result recalculates immediately, so you can weigh up options side by side.