No history yet
Sample Size Calculator
Determine the required sample size for your research surveys or statistical studies.
Study Parameters
Define your confidence and error thresholds.
Use 50% if the distribution is unknown.
Higher confidence levels and smaller errors require much larger samples.
Understanding the Sample Size Calculator
Determine the minimum number of respondents needed for a statistically significant survey. Calculate necessary sample sizes for both infinite and finite populations with adjustable confidence levels.
How to use the Sample Size Calculator
- 1Select your desired Confidence Level (95% is the academic and industry standard).
- 2Enter your maximum acceptable Margin of Error (e.g., 5% means results reflect reality ±5%).
- 3Input the Population Proportion. Use 50% if you don't have prior data, as it ensures the most robust sample size.
- 4Provide a Population Size if you are surveying a specific, limited group (e.g., employees at a single company).
Common Use Cases
The Maths Behind the Calculation
n = (Z² × p × (1-p)) / e²This tool uses Cochran's Formula for large populations and applies a Finite Population Correction (FPC) when you provide a specific population size.
Frequently Asked Questions
What is the Margin of Error?
It is the percentage by which your sample result might differ from the actual population value. A lower margin requires a significantly larger sample.
Why use a 95% Confidence Level?
It means that if you repeated the survey 100 times, 95 times the results would be within your margin of error. It is the widely accepted balance between precision and cost.
When should I enter a population size?
Only when the group you are surveying is small (usually under 20,000). For larger groups, the population size has a negligible effect on the required sample.
Regional Notice: United States
"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."