Confidence interval calculator
Estimate a 95% normal interval for an independent sample mean. Your inputs stay in this browser tab.
Your result
A little input. A useful result.
Your result will appear here.How to use confidence interval calculator
Estimate a 95% normal interval for an independent sample mean. This free tool runs locally after you choose to start.
- Enter your own values, or start with the visible example.
- Adjust numbers separated by commas or spaces as needed.
- Choose the action button. Review the result, then copy text or download a file when available.
- Choose Clear all when finished to remove inputs and results from the interface.
Limits, without the small print.
Uses mean ± 1.96 × sample SD / √n. Not a small-sample t interval; assumes independent observations and a suitable normal approximation.
One job runs at a time. You can cancel it; jobs stop after 30 seconds. Browser and device capabilities affect performance.
Understand the safeguards →A couple of useful answers.
Does confidence interval calculator upload my data?
No. This tool processes your input in a browser worker. Your text and files are not sent to an application server. The static host receives page and asset requests; see our privacy explanation.
Is this tool free for work and study?
Yes. No account, paid API, usage subscription or watermark fee is required. You remain responsible for your content rights and checking results. Hosting providers and their free tiers are separate from this open-source software.
What should I check before relying on the result?
Uses mean ± 1.96 × sample SD / √n. Not a small-sample t interval; assumes independent observations and a suitable normal approximation. Review important outputs against the source, especially financial, legal, identity, medical and research calculations.