Period Calendar
NewLast period + cycle length → next periods, ovulation day, fertile window; calendar view. Collects nothing, no account.
This tool runs entirely in your browser — nothing you type or upload is sent to a server.Liked it? Spare 10 seconds
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About this tool
Enter the first day of your last period and your cycle length: the next 3 periods, ovulation day and fertile window are marked on a calendar, and you see which cycle day today is. The pregnancy tab calculates the week, trimester, estimated due date and milestones from your last period.
No data goes to a server; dates are only remembered on this device and removed with "Clear". Calculations are calendar averages, not medical advice.
Frequently asked
Nowhere. Dates and cycle info are kept only in this device's browser storage; nothing is sent to a server, not even we can see it. "Clear" removes it.
14 days before the next period start (average luteal phase). The fertile window opens 5 days before ovulation and closes 1 day after. It varies by person.
Naegele's rule: first day of the last period + 280 days, adjusted if your cycle isn't 28 days. An ultrasound is more precise.
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