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Period & Ovulation Estimator
Estimate upcoming periods and a possible fertile window from cycle length.
Calendar estimates are uncertain, particularly with irregular cycles, and must not be used as contraception. Ovulation is modeled 14 days before the next period; the window is a rough six-day estimate. No dates or notes are saved.
Enter a valid calendar date
How to use Period & Ovulation Estimator
Enter your inputs above, choose the available mode, and review the results. Copy or download options appear where supported. These tools process your inputs in your browser.
Calendar estimates are uncertain, particularly with irregular cycles, and must not be used as contraception. Ovulation is modeled 14 days before the next period; the window is a rough six-day estimate. No dates or notes are saved.
Health results are general estimates and cannot establish a diagnosis or an individual treatment plan. Review important decisions with a qualified clinician.
Cycle reference: NHS: Periods.
Frequently asked questions
Are my inputs uploaded?+
No. These tools process entered text, numbers and selected files locally in your browser. Invoice templates are saved on your device only when you explicitly choose to save them.
Can I use this tool for free?+
Yes. No account is required. Estimates depend on your inputs and the assumptions explained on this page.