Ovulation Tracker
Track your fertile window and estimated ovulation date based on your last menstrual period. Helps with family planning. Health data never leaves your device — every calculation runs locally in your browser.
How to Use the Ovulation Tracker
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Frequently Asked Questions
How is the fertile window calculated?
Ovulation ≈ 14 days before the next period; the fertile window is the 5 days before plus ovulation day (sperm survive up to 5 days, the egg ~24h). Example: 28-day cycle starting May 1 → ovulation ≈ May 15, fertile May 10–16, next period ≈ May 29.
What if my cycle is irregular?
Calendar estimates weaken with irregularity — a 21–35 day range shifts ovulation by ±7 days. Track 3+ cycles to find your average, and confirm with basal-body-temperature or LH strips for conception timing.
Can this prevent pregnancy?
No — calendar method alone fails ~24% yearly with typical use. Ovulation shifts with stress and illness. Use barrier or hormonal contraception if avoiding pregnancy.
Does it predict the next period?
Yes, by adding your average cycle length to the last period start. Re-enter each cycle's actual start to keep predictions calibrated — every result uses only the dates just entered, nothing stored.
Is my cycle data stored?
No. All tracking runs locally in your browser. No health data is transmitted or stored.
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Last updated October 2026