Confidence Interval Calculator
Confidence interval for a mean given sample stats. This free online math calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
This calculator takes Sample Mean, Std Dev, Sample Size, and Z-score as input and computes Lower Bound and Upper Bound. The math runs entirely in your browser the moment you change a value — nothing is sent to a server, and your inputs are never stored.
The formula used is the standard math calculation for this metric. For a full step-by-step derivation with the default values, see the Worked Example section below.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Sample Mean: 50
- Std Dev: 10
- Sample Size: 30
- Z-score: 1.96
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
Frequently Asked Questions
What does the Confidence Interval Calculator compute?
The Confidence Interval Calculator takes 4 input values and returns 2 results. Confidence interval for a mean given sample stats.
Is my data sent to a server?
No. The Confidence Interval Calculator runs entirely in your browser using static JavaScript. Your inputs are never transmitted to CalculatorHive or any third party, and nothing is stored after you close the page.
Is this calculator free to use?
Yes. Every calculator on CalculatorHive is completely free. There is no signup, no paywall, and no usage limit. The site is supported by display advertising and affiliate partnerships, which are clearly labeled.
How accurate is the result?
The math is mathematically exact for the inputs you provide. Real-world accuracy depends on how accurately your inputs reflect the real situation — defaults are typical values, not guarantees.