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Cycle & Fertile Window Calculator
Estimate your next period, ovulation and fertile window. Everything is calculated in your browser — nothing you type is stored or sent anywhere.
Results update as you edit. The next estimated start is on or after today; earlier cycles are skipped.
Nothing leaves this page. The dates you enter are held in the page's memory and calculated on your device. There is no account, no request to a server, and nothing written to storage — close the tab and it is gone.
Estimates only. Calendar predictions assume a regular cycle and cannot account for illness, stress, medication or perimenopause. This is not contraception and not medical advice — for anything that matters, talk to a clinician.
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