Ovulation Calculator
Estimate your ovulation date and fertile window from your last period and cycle length, with predictions for the next three cycles.
This tool runs entirely in your browser.
How to use the Ovulation Calculator
- 1Enter the first day of your last period.
- 2Enter your average cycle length (and luteal phase if you know it).
- 3See your estimated ovulation day, fertile window and next period.
What is the Ovulation Calculator?
Ovulation usually happens about 14 days before the next period (the luteal phase), not necessarily on day 14 of the cycle. In a 32-day cycle it is about 18 days after the period starts.
The fertile window is the five days before ovulation plus the day after, because sperm can survive up to five days. The two days before ovulation and ovulation day itself are the most fertile.
Frequently asked questions
Can I use this for contraception?
No. Cycles vary and ovulation can shift, so calendar estimates are not reliable contraception.
Is the Ovulation Calculator free and private?
Yes. The Ovulation Calculator is free, needs no account, and runs entirely in your browser. What you type is never sent to a server or stored.
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