Confidence Interval Calculator
Compute confidence intervals for means — 95%, 99% or custom.
How to use Confidence Interval Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the sample mean, standard deviation and sample size.
- 2
Step 2. Choose a confidence level (90%, 95%, 99% or custom).
- 3
Step 3. See the confidence interval and margin of error.
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 confidence interval calculator.
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