Health & Fitness · Free tool
Ovulation Calculator
Find your estimated ovulation date and fertile window from the last period and cycle length. Free, private, 100% in-browser.
Ovulation day
May 6, 2026
Fertile window
May 1 – May 6, 2026
Next period
May 20, 2026
Cycle length
28 days
| Cycle | Fertile window | Ovulation | Next period |
|---|---|---|---|
| #1 | May 1 – May 6, 2026 | May 6, 2026 | May 20, 2026 |
| #2 | May 29 – Jun 3, 2026 | Jun 3, 2026 | Jun 17, 2026 |
| #3 | Jun 26 – Jul 1, 2026 | Jul 1, 2026 | Jul 15, 2026 |
How it works
- Ovulation is estimated at (cycle length − 14) days after the first day of your period.
- The fertile window covers the 5 days before ovulation plus ovulation day itself.
- Estimates only — track basal temp or use LH tests for accuracy.
What it does
Find your most fertile days from the date of your last period and your average cycle length. The tool estimates ovulation (around 14 days before your next period), the six-day fertile window leading up to it, and the predicted start of your next three cycles — useful whether you're trying to conceive or planning around your cycle.
This is a rhythm-based estimate; real ovulation varies by a few days from cycle to cycle. For higher accuracy combine with basal body temperature tracking or ovulation test strips. If you've already conceived, switch over to pregnancy calculator for due-date and week math.
How to use it
- Enter the first day of your last period.
- Enter your average cycle length (default 28 days).
- Review your predicted ovulation day and fertile window.
- Plan around the next three predicted cycles shown below.