Free Confidence Interval Calculator
Calculate confidence intervals for means and proportions at any confidence level.
Quick Answer
A 95% confidence interval means 95% probability the true value falls within the range. CI = mean ± (z × standard error).
Key Facts about Confidence Interval Calculator:
- 95% CI most common
- Higher confidence = wider interval
- Larger sample = narrower CI
- 95% uses z=1.96
- Margin of error = half CI width
Why Use Our Confidence Interval Calculator?
CI tools:
Multiple Levels
90%, 95%, 99% CI.
Means & Proportions
Both calculation types.
Sample Size
Account for n.
Margin of Error
Calculate MOE.
Instant
Quick results.
Private
Data stays secure.
How to Confidence Interval Calculator in 3 Easy Steps
Calculate CI:
Enter Data
Sample statistics.
Choose Level
Confidence level.
Get Interval
See CI range.
Why Use Our Calculator?
Multiple confidence levels
Means and proportions
Shows formula
Instant results
Frequently Asked Questions
Everything you need to know about our confidence interval calculator
What is 95% confidence interval?
95% probability true value is within the range.
It means 95% probability the true population value falls within the calculated range.
Still have questions? Try the tool yourself!
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