Period dates, fertile window & ovulation — calculated privately in your browser
100% Private — Zero Data Collection
All calculations happen locally in your browser. everykit never saves, transmits, or has access to your health data. This tool works entirely offline once loaded.
The first day of bleeding
Typical range: 20–45 days
How many days it lasts
Cycle timeline
PeriodFertile windowOvulation dayToday
Next 2 cycles — planning ahead
This calculator uses the standard formula (ovulation ≈ cycle length − 14 days from period start). Individual cycles vary. This tool is for informational purposes only and is not a substitute for medical advice or a reliable contraceptive method.