Ovulation Calculator
Estimate your fertile window, ovulation date, next period & due date.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Ovulation Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the first day of your last menstrual period.
- 2
Step 2. Pick your average cycle length (14–45 days).
- 3
Step 3. Read your estimated ovulation date, fertile window, next period and due date.
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Step 4. Review the timeline to see how the dates relate.
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 ovulation calculator.
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