How do I calculate confidence interval? Enter your numbers above and the result updates instantly. For example: Sample mean: 52 · Standard deviation: 8 · Sample size: 64 · Confidence level: 95 → 95% confidence interval: 50.04 to 53.96.
Is this Confidence Interval Calculator free? Yes — completely free with no sign-up or paywall. It runs entirely in your browser and keeps working offline; the numbers you enter never leave your device.
How accurate is it? It uses the standard published formula for confidence interval. Results are estimates for planning — not financial, tax, medical, engineering, or legal advice.