Period Calculator - Cycle Tracker
Predict your next period dates — enter your last period and cycle length to see your upcoming 6 periods estimated instantly.
Tool Interface
Your predicted periods
How to use
- Enter the first day of your last period.
- Enter your average cycle length (first day of one period to the day before the next — often 28).
- Enter your usual period length in days.
- Press Predict my periods to see your next 6 estimated period dates.
- Everything runs in your browser — no signup, nothing uploaded.
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About This Tool
Introduction: Know Your Dates in Advance
Trencada's free Period Calculator predicts your upcoming period dates from the first day of your last period and your average cycle length. See your next 6 estimated periods at a glance — useful for planning travel, events, and everyday life. All calculations happen instantly in your browser.
How to Use the Period Calculator
- Enter the first day of your last period using the date picker.
- Enter your average cycle length — the number of days from the first day of one period to the day before the next (often 28).
- Enter your usual period length in days.
- Press Predict my periods to see your next 6 estimated period dates, each with its estimated end date.
Key Features
- Next 6 periods predicted from your last period and average cycle
- Estimated end dates for each predicted period
- Clear "Next" highlight on your upcoming period
- Honest estimates: built-in note that cycles vary and this is not medical advice
- 100% private: your dates are calculated in your browser and never uploaded
Why Choose Trencada
Every Trencada tool is free forever with no accounts, no installation, and no hidden costs. The Period Calculator runs 100% in your browser — the dates you enter never leave your device.
Frequently Asked Questions
How accurate are the predictions?
They are estimates based on your average cycle length. Real cycles vary from month to month due to stress, travel, illness, and other factors — treat the dates as a guide, not a guarantee.
What is cycle length?
The number of days from the first day of one period to the day before your next period starts. The average is 28 days, but anything from 21 to 35 is common.
Is this medical advice?
No. This tool is for informational purposes only. If your periods are irregular, very painful, unusually heavy, or you have health concerns, please talk to a healthcare professional.
Is my information private?
Yes. Everything is calculated locally in your browser — nothing you enter is uploaded, stored, or tracked.