📊 Sample Size Calculator
Calculate required survey sample size
Use 50% if unknown (most conservative)
Required Sample Size
385
Step-by-step calculation
- 1.Formula: n = z² × p(1-p) / e²
- 2.Confidence level: 95% → z = 1.96
- 3.Margin of error: 5% = 0.05
- 4.Population proportion: 50% = 0.5
- 5.z² = 1.96² = 3.8416
- 6.p(1-p) = 0.5 × 0.50 = 0.2500
- 7.e² = 0.05² = 0.002500
- 8.n = 3.8416 × 0.2500 / 0.002500 = 384.16
- 9.Round up: n = 385
How Sample Size Is Determined
- 1Set the desired confidence level (e.g., 95%) and margin of error (e.g., ±5%).
- 2Enter the population size (or leave blank for a very large population).
- 3The calculator applies the formula n = (Z²·p·(1-p)) / E² with finite population correction.
About Sample Size Calculator
Determine the required sample size for surveys and experiments. Set confidence level, margin of error, and population size.
Frequently Asked Questions
What margin of error should I use?
±5% is standard for most surveys. Use ±3% or lower for high-precision research.
Does population size matter?
For large populations (>20,000), it barely affects the result. For smaller populations, a finite correction factor reduces the needed sample.