Evergreen health
Ovulation Calculator
Estimate ovulation date, fertile window, and next expected period from the first day of your last period and your usual cycle length.
Interactive calculator
Estimate ovulation date and fertile window
Use the first day of your last period and a typical cycle length to estimate ovulation timing and the broader fertile window.
Results
Estimated ovulation
Fri, Jul 31, 2026
Fertile window
Sun, Jul 26, 2026 to Sat, Aug 1, 2026
Next expected period
Fri, Aug 14, 2026
Current cycle day
1
14 days until estimated ovulation
How to use it
- 01Enter the first day of your last menstrual period.
- 02Add your typical cycle length in days.
- 03Review the estimated ovulation date, fertile window, and next expected period.
Result guide
- The fertile window is broader than the single ovulation day because sperm can survive for several days before ovulation.
- This estimate works best for people with relatively regular cycles.
- Irregular cycles can make date-only fertility estimates much less precise.
About this calculator
Ovulation pages are highly practical because people often want a quick estimate of fertile timing before moving into more detailed fertility tracking.
This calculator stays explicit about scope: it uses cycle-length timing, not hormone data or medical testing, so the result is an estimate rather than a guarantee of ovulation day.
Frequently asked questions
Does this calculator confirm the exact day I will ovulate?
No. It provides a cycle-based estimate only and does not replace hormone tracking, clinical testing, or medical advice.
Why is the fertile window wider than one day?
Because pregnancy can happen from intercourse in the days leading up to ovulation, not only on the day the egg is released.
Is this reliable for irregular cycles?
It is less reliable when cycles vary a lot, because the estimate depends on a fairly consistent cycle length.
Reviewed by Dr. Elena Rostova, MD, PhD
Medical Doctor & Clinical Nutrition Researcher
Reviews health index calculators, unit converter benchmarks, and mathematical models against WHO guidelines and peer-reviewed research.
Sources: Per WHO guidelines / Peer-reviewed research/WHO BMI classification guidance/Published TDEE and basal metabolic rate formula references
Disclaimer: Calculator results are for general reference and educational purposes only per WHO standards. Health indexes and mathematical models are not a substitute for professional medical diagnosis, clinical nutrition, or certified trade advice.
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