Confidence Level Calculator
Convert a z critical value into a two-sided confidence level, central area, and tail probabilities under the standard normal distribution.
Two-sided confidence level:
CL = 2Φ(z) − 1
| Metric | Value |
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Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
How it works
This tool uses the standard normal CDF to convert a z critical value into:
central confidence level, left-tail area, and right-tail area.
Examples
- z = 1.645 → about 90% confidence
- z = 1.96 → about 95% confidence
- z = 2.576 → about 99% confidence
When to use this tool
This tool is designed for quick, practical tasks such as everyday calculations, data formatting, or simple conversions. It is best used when you need fast results without installing software or using complex tools.
When to use
- Quick checks or one-time calculations
- Validating or converting data before using it elsewhere
- Simple tasks that do not require advanced software
When not to use
- Critical financial, legal, or medical decisions
- Large-scale or automated processing
- Situations requiring guaranteed precision beyond basic validation
Always review results before using them in important contexts.
About this tool
This tool helps you perform quick utility operations directly in your browser. It runs entirely in your browser without sending data to a server.
You can use this tool when handling simple tasks without installing additional software. The results should be interpreted as a processed output based on your input data.
FAQ
- What does this confidence level calculator compute?
It converts a z critical value into the corresponding two-sided confidence level and tail areas under the standard normal distribution.
- What is a z critical value?
It is the cutoff value on the standard normal distribution used for constructing confidence intervals.
- Is this for two-sided confidence intervals?
Yes. This calculator interprets the input z value as a symmetric two-sided confidence interval cutoff.
- Are calculations stored?
No. Everything runs locally in your browser.