Statistics & Probability Calculators
Margin of Error Calculator
Compute the margin of error E = critical × σ ÷ √n for a chosen confidence level.
Loading tool…
What is Margin of Error?
The margin of error is the half-width of a confidence interval: how far the estimate could plausibly be from the truth at the chosen confidence. It is the critical value times the standard error, E = z* × σ ÷ √n.
How it works
The critical value is chosen from the t table for small samples and the normal z for larger ones, then multiplied by σ ÷ √n. The margin of error is shown alongside the standard error it came from, and the large-sample z value for the confidence level is printed for comparison.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.