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Ovulation Calculator
ovulation · fertility · cycle · 排卵日 · 배란일
Calendar estimate · not a contraceptive method, not medical advice.
How to use
- 1
Enter the first day of your last period.
- 2
Enter your cycle length.
- 3
See the estimated ovulation and fertile window.
FAQ
Is this tool free?
Yes — no sign-up, no installation, completely free to use right away.
What is this tool?
This tool estimates your fertile window and likely ovulation days from your cycle. It's useful for family planning or simply understanding your body better. The dates aren't stored and it runs in your browser.
Can I use it for contraception?
No — this is a calendar estimate, not a contraceptive method.