🩸Period Calculator
Predict your next period dates.
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About this calculator
Free Period Calculator — predict your next period dates from your last period and average cycle length.
How to use
Enter your First Day of Last Period, Cycle Length above — the result updates instantly as you type or drag the sliders. It's free and needs no sign-up.
Frequently Asked Questions
What does the Period Calculator do? ▼
Predict your next period dates.
How do I use the Period Calculator? ▼
Enter your values using the input fields or sliders. The result updates instantly — no submit button needed. All calculations run in your browser.
How accurate is the Period Calculator? ▼
The Period Calculator uses standard mathematical formulas and the inputs you provide. Results are estimates meant to guide decisions — consult a qualified professional for advice specific to your situation.
Who should use the Period Calculator? ▼
The Period Calculator is designed for healthy adults as a general guide. Results may not apply to children, pregnant people, athletes, or those with specific medical conditions.
Should I consult a professional about my Period Calculator results? ▼
The Period Calculator is for general information and self-education only. For medical, health, or treatment decisions, always consult a qualified doctor or healthcare professional.
Is the Period Calculator free? ▼
Yes — completely free. No sign-up, no download, and no account required. Works in any browser.