July 2026
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Period / menstrual cycle calculator
Predict your next period, ovulation date, and likely fertile window.
Estimate, not a diagnosis. This tool gives an educational estimate based on the numbers you enter. It cannot account for your individual health history — consult a healthcare professional for anything clinical.
How this works
We use the first day of your last period and your average cycle length to estimate your next period by adding the cycle length. Ovulation is estimated as 14 days before the next period (a typical luteal phase), and the fertile window is the five days before ovulation plus ovulation day itself.
Outputs
- Predicted next period date
- Estimated ovulation date
- Fertile window
Limitations
This is an estimate suitable for planning. Irregular cycles, hormonal contraception, pregnancy, and medical conditions can make predictions unreliable. For clinical decisions, consult your healthcare provider.