PALLAS / CALCULATOR
Sample Size Calculator
Estimate the minimum sample size for a single proportion from confidence level, margin of error and expected proportion, with optional design effect and finite-population correction.
INPUT
Enter values
Method & formula
This tool estimates sample size for a single proportion. It uses the selected two-sided normal critical value, expected proportion and absolute margin of error; an optional finite-population correction reduces the requirement when the target population is known and not very large.
- n₀ = DEFF × z² × p × (1 - p) / e²
- Finite population: n = n₀ / (1 + (n₀ - 1) / N)
- Final sample size is rounded up
Example
At 95% confidence, 5% margin of error, p = 50% and no finite-population correction, the required sample size is 385.
Sources & standards
FAQ
Is this a power calculator for clinical trials?
No. It estimates sample size for a single proportion. Comparative studies, hypothesis tests and power calculations need different models.
Why is 50% the default proportion?
For this formula, p = 50% gives the largest p(1-p) term and therefore a conservative sample size when no prior estimate is available.