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Both calculators run independently — change the inputs on either side to compare results.

Standard Error Calculator

Compute the standard error of the mean (SEM) from the sample standard deviation and sample size, SEM = s/√n. Quantifies how precisely a sample mean estimates the underlying population mean — the foundation of confidence intervals, t-tests, and any inferential statistic.

Standard Deviation

Sample Size

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Statistics

Confidence Interval Calculator

Compute the margin of error around a sample mean for a 90%, 95%, or 99% confidence interval using the z-distribution. The half-width of the CI tells you how precisely your sample estimates the population mean — essential for survey reporting, scientific publication, and any inference.

Sample Size (n)

Standard Deviation

Confidence Level

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Key differences

	Standard Error Calculator	Confidence Interval Calculator
Category	Statistics	Statistics
Inputs required	2	3
Result	Standard Error	Margin of Error (±)
What it does	Compute the standard error of the mean (SEM) from the sample standard deviation and sample size, SEM = s/√n. Quantifies how precisely a sample mean estimates the underlying population mean — the foundation of confidence intervals, t-tests, and any inferential statistic.	Compute the margin of error around a sample mean for a 90%, 95%, or 99% confidence interval using the z-distribution. The half-width of the CI tells you how precisely your sample estimates the population mean — essential for survey reporting, scientific publication, and any inference.