Period Calculator
Track and predict your menstrual cycle, period dates, and PMS windows.
How Period Tracking Works
This calculator uses your last period date, average cycle length, and period length to predict future menstrual cycles. Ovulation is estimated to occur 14 days before the next period, and the PMS window is the 5 days before the period starts.
Menstrual Cycle Phases
- Menstrual Phase: Days 1-5 (varies) — Uterine lining sheds.
- Follicular Phase: Day 1 to ovulation — Follicles mature in the ovaries.
- Ovulation: Around day 14 before next period — Egg is released.
- Luteal Phase: Ovulation to next period — Usually 14 days fixed.
About this Calculator
The Period Calculator is a free, easy-to-use tool for menstrual, cycle, PMS. Simply enter your values and get instant, accurate results — no signup, no ads, no tracking. All calculations run locally in your browser, so your data stays completely private.
Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.