Math Calculators
Sample Size Calculator
Find the survey sample size you need.
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Result
Required sample size
271
About the Sample Size Calculator
How many people do you need to survey for reliable results? Enter your confidence level, acceptable margin of error, and (optionally) the population size, and the calculator returns the required sample size using Cochran's formula. It's essential for planning surveys, polls, and experiments that need statistically valid results.
How to use the Sample Size Calculator
- 1Enter your confidence level, margin of error, and population size.
- 2Read the result instantly — it recalculates as you type.
- 3Adjust the numbers to model different scenarios.
Frequently asked questions
How big should my sample be?
It depends on your confidence level and margin of error. For a 95% confidence and ±5% margin, about 385 responses suffice for a large population.
Do I need the population size?
Only for smaller populations. For large or unknown populations, leave it at 0 and the tool uses the infinite-population formula.