Confidence Interval Calculator (Mean)
Math ToolsMargin of error and range for a sample mean
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History
All history →Confidence Interval Calculator (Mean) — at a glance
Get the likely range for the true average.
How to use it — step by step
Sample mean, standard deviation, sample size and confidence level.
Enter your values
Fill in the fields. Default numbers are shown so you can see how it works.
Press Calculate Interval
The answer appears at once as large result cards.
Copy or share
Copy the result, or share a link that opens with your numbers filled in.
Pro tips
Small things that make the result better.
Quick facts
Frequently Asked Questions
What does 95% confidence mean?+
If you repeated the study many times, about 95% of the intervals would contain the true mean.
What if n is small?+
For small samples a t value is better. This tool uses z.
Is my data safe?+
Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.
Is this tool really free?+
Yes — completely free, no signup, no watermark and no usage limit.