Understand the method before using any result. The details below describe the purpose and assumptions for this tool.
How the confidence interval calculator works
The confidence interval calculator helps you estimate results using the assumptions and values you provide. Review the formula and example before relying on the result.
Formula and assumptions
Approximate confidence interval = sample mean ± critical z × sample standard deviation ÷ square root of sample size.
Example
Example: use the default values, calculate once, then change one input at a time to see how the result changes. Verify important results independently.
Important information
Results depend on the values, jurisdiction, date and assumptions you enter. Financial products, tax rules and medical recommendations may vary by location and change over time. Verify critical results with reliable sources.