General Math Calculators
Confidence Interval Calculator
Confidence Interval Calculator calculate a confidence interval for a mean from mean, standard deviation, sample size, and confidence level.
General Math Calculators
Confidence Interval Calculator
Calculate a confidence interval for a mean from mean, standard deviation, sample size, and confidence level.
Formula
Mean CI = sample mean +/- t critical * sample SD / sqrt(n), where df = n - 1.
About the Confidence Interval Calculator
Calculate a confidence interval for a mean from mean, standard deviation, sample size, and confidence level. General math calculators apply the named arithmetic, algebraic, combinatorial, percentage, or summary equation to the entered values.
How the Confidence Interval Calculator Works
Mean CI = sample mean +/- t critical * sample SD / sqrt(n), where df = n - 1.
The calculation runs in your browser. Submitted values are validated for the required numeric range, data shape, units, and method-specific restrictions before a result is shown.
Required Inputs
- Sample mean (required)
- Sample standard deviation (required)
- Sample size (required)
- Confidence level percent (required)
Results Reported
The result panel shows the final answer together with the intermediate quantities needed to audit the calculation. Depending on this method, reported values include:
sample_meansample_sdsample_sizedfconfidence_levelstandard_errorcritical_valuemargin_of_errorlower_boundupper_bound
Confidence Interval Calculator Example
Use the example data button, calculate, and review the formula and worked solution before using the result.
| Input | Example value |
|---|---|
| Sample mean | 50 |
| Sample standard deviation | 10 |
| Sample size | 25 |
| Confidence level percent | 95 |
How to Use the Calculator
- Confirm that the calculator title and method match the quantity, test, conversion, or planning question you need to solve.
- Enter values with compatible units and the requested sample, group, matrix, count, date, or option format.
- Select Example Data to inspect a valid input layout, or enter your own values and select Calculate.
- Review the result table, formula, worked substitutions, warnings, and interpretation rather than using only the headline number.
- Use Copy Result or Download CSV when you need a reusable record of the displayed calculation.
Understanding the Result
Check domain restrictions, units, sign conventions, rounding, and whether the result should be interpreted as an exact value or an approximation.
Keep the entered values, units, selected options, and any warning shown beside the result. For a hypothesis test, report the statistic, degrees of freedom where applicable, p-value, alpha level, effect size, and decision. For an estimate or conversion, report the formula convention and final unit.
Accuracy and Limitations
The calculator keeps full browser precision during calculation and rounds only for display. Accuracy still depends on correct inputs and on whether the displayed model represents the real problem. Educational calculators cannot replace required professional review, current official rules, field measurements, laboratory methods, or specialist statistical software where those are necessary.
Frequently Asked Questions
What does the Confidence Interval Calculator calculate?
Calculate a confidence interval for a mean from mean, standard deviation, sample size, and confidence level.
Which formula does the Confidence Interval Calculator use?
Mean CI = sample mean +/- t critical * sample SD / sqrt(n), where df = n - 1.
What does this calculator show?
It shows the entered values, the formula used, calculated variables, and the final answer.
What should I check before using the result?
Confirm the inputs, units, selected mode, domain restrictions, and displayed formula match the problem you need to solve.