Menstrual Cycle Calculator
Next 6 periods, ovulation dates and fertile windows.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Menstrual Cycle Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the first day of your last period.
- 2
Step 2. Enter your average cycle length in days.
- 3
Step 3. Enter your typical period length.
- 4
Step 4. Read the next 6 cycles with period start/end, ovulation and fertile window.
Why use this tool
Private by design
All processing happens locally in your browser. Open DevTools → Network and you'll see zero file uploads. Ever.
Instant
No upload wait, no queue, no server round-trip. Results appear the moment you drop a file.
Free & unlimited
No accounts, no watermarks, no daily caps. Use it as many times as you like, forever.
Works everywhere
Desktop, tablet or phone — every tool is responsive and installable as a PWA for offline use.
Frequently asked questions
Everything you might want to know about menstrual cycle calculator.
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