Period Calculator
Predict your next period, fertile window and ovulation from LMP and cycle length. Calendar of the next 3 cycles; estimate only, private and offline.
Average cycle, typically 28 days (20–45)
Enter your last menstrual period date to calculate the next period.
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About the author
Written and maintained by the Tool4SaaS team. Every tool runs locally in your browser and is tested in-house for accuracy. Last updated: .
Frequently asked questions
Next period = LMP + cycle length; ovulation ≈ LMP + (cycle−14).
No, for informational purposes only. Consult a healthcare professional for personal guidance.
Yes, it is free, works offline in your browser, and your data never leaves your device.
How to use Period Calculator
- Enter LMP: Pick last period start date.
- Set cycle: Enter average cycle length.
- View: See next periods and fertile days.