MihsabaHow to use
Sample-size planning estimates the minimum number of observations needed for a target confidence level and margin of error when estimating a proportion or mean under simple random sampling.
- Choose proportion or mean.
- Set confidence level and margin of error, then p for a proportion or σ for a mean.
- Optionally enter finite population size and use the final result rounded up.
How it is calculated
Example
For an unknown proportion at 95% confidence and ±5 percentage-point margin, p=0.5 gives n₀≈384.15, so 385 completed responses are required before any finite-population correction.
Important notes
This is a margin-of-error sample-size calculator, not a statistical-power calculator for hypothesis testing. Clustered, stratified or nonresponse-adjusted designs can require additional corrections.
Frequently asked questions
Why use p=0.5 when the proportion is unknown?
It maximizes p(1−p) and therefore gives the most conservative proportion sample size.
Why round up?
A fractional sample cannot meet the target; the next whole observation is required.
When should I use finite-population correction?
When the total population is known and bounded and sampling is effectively without replacement.
Is this calculator free?
Yes. It is free to use and requires no account.