Menstrual Cycle Length Calculator
Average cycle length, regularity and next period.
Your result
Your cycles are regular, within the typical 21–35 day range with variation under 7 days.
Medical disclaimer: This tool is for education and is not medical advice. Read more.
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Find this tool when you want to:
Learn more
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Frequently asked questions
What does the Menstrual Cycle Length Calculator do?
Average cycle length, regularity and next period. Enter your values and the result and chart update instantly.
How accurate is it?
It uses published, widely used formulas. Results are estimates for education and planning, not a diagnosis. Talk to a qualified clinician about decisions affecting your health.
Is my information stored or shared?
No. All calculations run in your browser and nothing you type is sent to a server or saved.
What can I search to find this tool?
People find it by searching for: is my period regular; predict next period; irregular cycle.