Sample Size: 95% Confidence, 10% Margin of Error
A larger 10% margin of error with 95% confidence and p = 0.5 only requires a sample size of 97.
How to use this tool
- Enter expected proportion (p), z* (confidence level) and margin of error (e) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your required sample size (n) and the full breakdown beneath it.
See how a wider acceptable margin of error dramatically reduces the required sample size for a 95% confidence survey.
Frequently asked questions
- Why use p = 0.5 when the proportion is unknown?
- p × (1−p) is maximised at p = 0.5, giving the most conservative (largest) required sample size. If you have a prior estimate of p, use it to get a smaller required n.