🌼 Period Calculator
Enter the first day of your last period and cycle length to predict the next 6 periods, the ovulation day and fertile window. Personal health reference, local, no upload.
❓ Frequently asked questions
How is ovulation estimated?
As cycle length minus 14 (the luteal phase is usually ~14 days).
What is the fertile window?
About 5 days before to 1 day after ovulation - the higher-conception window.
Is it accurate?
A reference for regular cycles only; real timing varies with stress and health.
📚 How to use
Knowing your cycle helps with planning or trying to conceive.
Steps
- Enter the first day of your last period and cycle length.
- Click "Predict".
- See upcoming periods, ovulation and fertile window.
About this tool
Period tracking shouldn't require an account and a data harvest.
This calculator estimates your next period and cycle window from a few dates, so you can plan without handing an app your whole life.
Handy before a trip, a race, or just to know what's coming.
Runs on your device; your dates aren't uploaded.
Honest note: it's a calculator, not medical advice — talk to a clinician about real health questions. (We keep no data; anonymous analytics only — privacy policy.)
Tip: log a few months to sharpen the estimate; one cycle alone is a guess. Hope it helps.