Average Cycle Length Calculator
Use this free average cycle length calculator to find your average menstrual cycle length and how regular it is.
Health information notice: Results are estimates based on general formulas and may not reflect individual circumstances. This tool is not a diagnosis or substitute for personalized advice from a qualified healthcare professional.
How the average cycle length calculator works
Average = sum of cycle lengths ÷ number of cycles. A range of 7 days or less between your shortest and longest cycles is usually considered regular.
Frequently asked questions
What is a normal cycle length?
Most cycles are 21–35 days. See a doctor if your cycles are consistently outside that or change suddenly.
Results are estimates for general information only. They are not a substitute for professional advice where applicable. Found a mistake? Report an error.