Z-Score Calculator
z = (x − μ) / σ — with percentile and tail probability.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Z-Score Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the value x you want to test.
- 2
Step 2. Enter the mean μ and the standard deviation σ (must be positive).
- 3
Step 3. See the z-score, percentile and tail probabilities update instantly.
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 z-score calculator.
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