Period Predictor
Enter at least 2 previous start dates to predict the next 12 cycles.
Enter at least 2 previous start dates to predict the next 12 cycles.
Predict the next 12 menstrual period start dates by entering two or three recent cycle dates. The tool calculates your average cycle length and projects future dates so you can plan ahead with confidence.
Period Predictor is a free, browser-based menstrual cycle calculator that estimates your next 12 period start dates. It works by averaging the gap between the cycle dates you provide and projecting that interval forward. No account is needed and no personal data is stored on any server. All calculations happen locally in your browser, ensuring complete privacy. The tool accepts two or three past start dates for greater accuracy and flags results if the cycle data appears outside typical ranges.
Enter the start date of your two most recent periods in the date fields provided. Optionally add a third date for improved accuracy. Click the Predict button and the tool instantly calculates your average cycle length, then generates 12 projected start dates into the future. Results are displayed clearly on screen with your estimated cycle length shown at the top. You can print the results or save them as a PDF directly from the page for personal records or to share with a healthcare provider.