Period Calculator
Feed it your last period start and average stats; receive the next several predicted cycles.
How the Period Calculator works
The calculation follows the standard method used across the US — no shortcuts, no hidden assumptions. Here is exactly what happens behind the scenes:
Frequently Asked Questions
How does the Period Calculator work?
Enter your numbers above and results update instantly using standard formulas, computed entirely on your device.
Is the Period Calculator free to use?
Yes — completely free with no signup required, and it works on phones, tablets, and desktops.
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