Ovulation Calculator
Estimate your ovulation day and most fertile window from your last period and cycle length, plus your next three period dates. Free, private ovulation and period calculator.
How to use the Ovulation Calculator
- 1
Enter the first day of your last period.
- 2
Set your average cycle length.
- 3
See your estimated ovulation day and fertile window.
- 4
Check your next three predicted period dates.
Frequently asked questions
How is ovulation estimated?
For a regular cycle, ovulation is about 14 days before your next period, and the fertile window spans the ~5 days before ovulation through the day after.
Can I use this for birth control?
No — cycle timing varies and this is not a reliable contraceptive method. Use it for general awareness only.
Is my data private?
Yes — everything is calculated in your browser and nothing is stored.
Tips & discussion
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