Sample Size Calculator
Calculate sample size using your data.
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What this tool does
Calculate sample size using your data. Simple random sample for estimating a proportion; p=50% is conservative. No clustering/design-effect adjustment.
How to use the Sample Size Calculator
- Enter or select population size (0 = unlimited).
- Enter or select confidence level.
- Enter or select margin of error (percentage points).
- Enter or select estimated population proportion (%).
- Read the calculated result; change any measurement to compare alternatives.
Formula
n0=z²×p×(1−p)/e²; finite-population n=n0/(1+(n0−1)/N); round up
- population
- Population size (0 = unlimited)
- confidence
- Confidence level
- margin
- Margin of error (percentage points)
- p
- Estimated population proportion (%)
Simple random sample for estimating a proportion; p=50% is conservative. No clustering/design-effect adjustment.
Worked example
For sample size calculator, the following measurements illustrate the exact method: Population size (0 = unlimited): 10000; Confidence level: 95; Margin of error (percentage points): 5; Estimated population proportion (%): 50.
Inputs
- Population size (0 = unlimited)10000
- Confidence level95%
- Margin of error (percentage points)5
- Estimated population proportion (%)50
Result
- Required sample size370
Results explained
- Required sample size
- Required sample size from the formula above. Simple random sample for estimating a proportion; p=50% is conservative. No clustering/design-effect adjustment.
Frequently asked questions
n0=z²×p×(1−p)/e²; finite-population n=n0/(1+(n0−1)/N); round up
Simple random sample for estimating a proportion; p=50% is conservative. No clustering/design-effect adjustment.
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.