Menstrual Cycle / Period Tracker Calculator
Estimate your next period date, PMS window, and fertile window based on your last period and cycle length.
A simple planning tool.
Your data stays in your browser. We do not store, collect, or transmit any information you enter.
Cycle Predictions
Menstrual cycle predictions are based on average cycle length patterns.
Key calculations:
Next Period = Last Period Start + Cycle LengthOvulation ≈ Next Period - 14 daysFertile Window ≈ Ovulation Day - 5 to Ovulation Day + 1PMS Window ≈ 7-10 days before next period
Average cycle facts:
- Average cycle length: 28 days (normal range: 21–35 days)
- Average period duration: 3–7 days
- Ovulation typically occurs 12–16 days before the next period
Important: This calculator provides estimates only. Cycles can vary month to month due to stress, illness, exercise, and other factors. It is not a reliable method of contraception. Consult a healthcare provider for medical advice.