Evergreen health
Menstrual Cycle Calculator
Track next expected period, estimated fertile window, cycle day, and current cycle phase from your last period date and usual cycle length.
Interactive calculator
Track next period and current cycle phase
Estimate your next period start, period end date, fertile window, and current cycle phase from the last period date and your usual cycle pattern.
Results
Next period
Fri, Aug 14, 2026
Period end
Tue, Jul 21, 2026
Current phase
Period
Cycle day 1
Fertile window
Sun, Jul 26, 2026 to Sat, Aug 1, 2026
28 days until next expected period
How to use it
- 01Enter the first day of your last period.
- 02Set the usual cycle length and the typical period length.
- 03Review the next expected period, fertile window, and current cycle phase.
Result guide
- Cycle-day and phase estimates depend on the dates and pattern you enter.
- The fertile window is an estimate and should not be treated as an exact clinical ovulation confirmation.
- Large cycle variation reduces precision for all date-based cycle trackers.
About this calculator
Cycle calculators work well because they give users a lightweight planning tool for travel, fertility timing, and symptom tracking without needing a full app account.
This version focuses on pattern-based estimation and labels the current phase clearly, so it stays useful without pretending to replace a medical cycle workup.
Frequently asked questions
What is the difference between this and the ovulation calculator?
This page adds next-period and current-phase tracking, while the ovulation calculator focuses more directly on fertile timing.
Can this diagnose cycle problems?
No. It is a date-based planner, not a diagnostic tool for irregular or painful cycles.
Why do I need a period length field?
It helps estimate the period end date and gives a more useful current-phase view for planning.
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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