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.
Mean 50
SD 10
n 100
Calculate Interval
Confidence interval
How to use it — step by step
Sample mean, standard deviation, sample size and confidence level.
1
Enter your values
Fill in the fields. Default numbers are shown so you can see how it works.
2
Press Calculate Interval
The answer appears at once as large result cards.
3
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.
✦Bigger samples give narrower intervals.
✦This uses the z value, so use n of 30 or more.
✦95% is the most common level.
Quick facts
Freeno signup
Privateruns in your browser
Instantresult in a second
No limituse it as often as you like
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.
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