Sample Size Calculator
Calculate the minimum sample size required for your survey or research study. Enter your desired confidence level, margin of error, and expected proportion to find out how many respondents you need.
The sample size formula for estimating a population proportion is:
n = (z² × p × (1-p)) / e²
Where:
- z = z-score for the confidence level
- p = expected proportion (use 0.5 if unknown)
- e = margin of error (as a decimal)
Finite Population Correction:
If your population is small, apply: n_adj = n / (1 + (n-1)/N)
Using p = 0.5 gives the largest (most conservative) sample size because p(1-p) is maximized at 0.25.