Period Tracker Calculator
A simple calendar estimate of your next period and a rough ovulation date from your last period start. It does not read hormone levels or ultrasound data—use strips, temperature logs, or clinician care if you need clinical precision.
- Last period start: Day 1 is the first noticeable bleeding of the cycle you want to base the math on.
- Earlier period (optional): If you add another recent Day-1 date, we infer your average cycle length from the gap between the two.
- Manual cycle length: Used only if you don't supply two dates — your typical full cycle length in days (often 24–35).
Pick the first day of bleeding for the cycle you’re tracking.
Improves the average cycle length when your cycles are uneven week to week.
Only used when a second period date is not provided.
Choose the start date of your latest period to see estimates.
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If your flow is unusually heavy, try the period flow estimator, or the fertility timing helper for calendar-based planning.
Important usage notes & limitations
Reproductive timelines interact with contraception cessation, PCOS phenotype, transgender hormone therapy intensity, low body-fat athletic amenorrhea, and perimenopause. Hormonal contraception intentionally suppresses natural ovulatory signals until washout stabilization — calendar methods become meaningful only once cycles resume reliably.
See also: Pregnancy Due Date Calculator · Women's health calculators hub.