Why use this calculator
Proper sample size ensures your survey or study results are statistically reliable. Too small a sample wastes effort with inconclusive results; too large wastes resources.
How to use it
Select your desired confidence level, acceptable margin of error, and total population size. The calculator determines the minimum sample size needed.
The formula
n = (Z² × p(1-p)) / e² adjusted for finite population: n_adj = n / (1 + (n-1)/N).
Worked examples
95% confidence, 5% margin, population of 10,000
370 respondents needed
When people use it
- Survey design
- Market research
- Academic research
- Quality control sampling
Tips
- Lower margin of error requires larger samples
- Higher confidence requires larger samples
- For populations over 100,000, population size barely affects sample size
Questions people ask
- What confidence level should I use?
- 95% is the most common standard. Use 99% for critical decisions (medical, safety). 90% may be acceptable for preliminary or exploratory research.