Menstrual Period Calculator
Track your menstrual cycle and predict your next period, ovulation date, and fertile window. Essential for family planning or period tracking.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Next Period In
14 days
How to Use This Calculator
- Enter Days Since Last Period Started, Average Cycle Length, and Period Duration.
- Review the Next Period In (days) result.
- Use Ovulation In (days) and Fertile Window Starts In (days) to inform your decision.
- Use the chart to visualize the results and explore different scenarios by adjusting inputs.
How the result changes with Average Cycle Length
| Average Cycle Length | Next Period In |
|---|---|
| 23 | 9 days |
| 29 | 15 days |
| 36 | 22 days |
| 43 | 29 days |
What each input means
- Days Since Last Period Started
- How many days ago did your last period start?
- Average Cycle Length
- Number of days from the start of one period to the start of the next.
- Period Duration
- How many days does your period typically last?
How this is calculated
Worked example, using the default values
- Identify Input ParametersDays Since Last Period Started = 14, Average Cycle Length = 28, Period Duration = 5 = 3 input(s) provided
- Calculate Next Period In14 = 14
- Calculate Ovulation In28 = 28
- Calculate Fertile Window Starts In23 = 23
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
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