Women's health literacy
Cycle estimator
Project an approximate next period from your last start date and average cycle length. Not birth control.
Enter last period start and a cycle length between 21 and 45 days.
What this result means
This estimator projects an approximate next period start from your last period start date and average cycle length. It is a planning aid for awareness — not contraception and not a fertility diagnosis.
Cycle length commonly varies. Stress, illness, travel, thyroid issues, perimenopause, and some medications change timing.
How we calculate it
- Next period estimate ≈ last period start + average cycle length (days).
- Optional fertile-window education uses a simplified mid-cycle illustration only — not a birth-control method.
Limitations
- Not emergency contraception guidance and not IVF/fertility treatment advice.
- Unpredictable bleeding needs clinical evaluation.
- Do not use this tool alone to prevent or achieve pregnancy.
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Sources / References
Educational estimate only — not diagnosis, treatment, or medication dosing. See our medical disclaimer and editorial policy.