Confidence Interval Calculator

Added 2026-08-29

Calculate a t-based confidence interval for a sample mean or a Wilson confidence interval for a proportion.

✓ Runs locally in your browser✓ No account or dataset upload required✓ Effect sizes / uncertainty shown where appropriate

Interval for

Sample values (mean mode)Numbers may be separated by commas, spaces, semicolons or new lines.

Successes (proportion mode)

Total n (proportion mode)

Confidence level

Estimate

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Lower bound

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Upper bound

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Standard error / method

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Statistical output is a calculation aid. Check assumptions, study design and reporting requirements before drawing scientific conclusions.

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About this tool

Calculate a t-based confidence interval for a sample mean or a Wilson confidence interval for a proportion.

Common uses

95 confidence interval calculatormean confidence intervalproportion confidence intervalci calculator statistics

How it works

1Enter or paste the requested sample values, summary inputs or contingency data.
2Choose the method, confidence level or test options when available, then run the calculation.
3Review the estimate/test statistic together with p-value, confidence interval, effect size and method notes where available.

Frequently asked questions

Does this statistics calculation upload my data?

No. Entered values are processed locally in your browser with JavaScript.

Should I interpret statistical significance by itself?

No. Review effect size, confidence intervals, study design, assumptions, sampling and multiplicity together with the p-value.

Which interval methods are used?

Means use the Student t distribution from raw sample values. Proportions use the Wilson score interval, which behaves better than the simple Wald interval near 0 or 1.

Confidence Interval Calculator

How it works

Frequently asked questions

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