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Menstrual Cycle Length Calculator

Estimate average cycle length and identify expected fertile days.

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Clinical Accuracy

Grade A

Enter Your Recent Cycle Lengths

Enter the length of your last 3–6 cycles in days. First three are required.

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Research Reference

biotechScientific Method

Average cycle is computed from up to six recent cycle lengths, with normal reference range 21-35 days.

Munster K et al. (1992)

Int J Epidemiol.

PMID: 1623118Read paperopen_in_new