Free Cycle Calculators — Ovulation, Period & Due Date
A free, privacy-first menstrual cycle toolkit: calculate your safe and fertile windows, ovulation day, period dates, and estimated due date. Everything runs in your browser — your data never leaves your device.
Key Features
Ovulation Calculator
Estimate your fertile window and ovulation day from your cycle length and last period.
Safe & Fertile Windows
See your safe days and high-fertility days at a glance on a clear cycle timeline.
Period & Cycle Tracking
Predict upcoming periods and understand your personal cycle rhythm over time.
Due Date Estimator
Get an estimated due date and key milestones from your last period.
Privacy by Design
All calculations happen locally in your browser — nothing is uploaded or stored on a server.
Free & No Sign-Up
Every calculator is completely free to use, with no account required.
Who It's For
Anyone tracking their menstrual cycle, planning ahead, or learning about reproductive health