Margin of Error Calculator
Calculate margin of error using your data.
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What this tool does
Calculate margin of error using your data. Normal approximation for an independent random sample proportion, no finite-population correction.
How to use the Margin of Error Calculator
- Enter or select sample size.
- Enter or select confidence level.
- Enter or select observed proportion (%).
- Read the calculated result; change any measurement to compare alternatives.
Formula
margin percentage points=100×z×sqrt(p×(1−p)/n)
- sample
- Sample size
- confidence
- Confidence level
- p
- Observed proportion (%)
Normal approximation for an independent random sample proportion, no finite-population correction.
Worked example
For margin of error calculator, the following measurements illustrate the exact method: Sample size: 400; Confidence level: 95; Observed proportion (%): 50.
Inputs
- Sample size400
- Confidence level95%
- Observed proportion (%)50
Result
- Margin of error (percentage points)4.9
Results explained
- Margin of error (percentage points)
- Margin of error (percentage points) from the formula above. Normal approximation for an independent random sample proportion, no finite-population correction.
Frequently asked questions
margin percentage points=100×z×sqrt(p×(1−p)/n)
Normal approximation for an independent random sample proportion, no finite-population correction.
Enter numbers only, separated as described in the labels. Check sample units and remove missing values rather than substituting zero.
No. Statistical inference depends on sampling design, independence, model fit and interpretation; a p-value is not the probability that a hypothesis is true.
No. Calculations and numerical distribution algorithms run entirely in the browser.