Sample Size Calculator
Estimate the sample size needed for a proportion using confidence level, margin of error, expected proportion, and optional finite population size.
Formula without finite population correction:
n₀ = z² · p(1-p) / E²
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Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
How it works
This tool estimates sample size for a proportion. If population size is provided, it also applies finite population correction.
Examples
- 95% confidence, 5% margin, p = 0.5
- Without population correction, this is a common survey planning setup
- Providing population size can reduce the required sample size
FAQ
- What does this sample size calculator estimate?
It estimates the sample size needed for a proportion using confidence level, margin of error, and expected proportion.
- What if I do not know the expected proportion?
A common conservative choice is 0.5 because it usually produces the largest required sample size.
- What is finite population correction?
If you provide a population size, the calculator applies a finite population correction to reduce the required sample size when the population is not very large.
- Are calculations stored?
No. Everything runs locally in your browser.