±Free
Proportion sample size
Estimate sample size for a proportion using z²p(1−p)/e², with optional finite population correction.
Enter p, the absolute margin e and a positive z value. The tool starts with n = z²p(1−p)/e², optionally applies the supplied finite population correction, and rounds the adjusted size upward.
How to use
- Enter your text, values, or image.
- Adjust the options and run the tool.
- Copy or download your result.
Worked example
Example input
Expected proportion (0–1): 0.5 Absolute margin (0–1): 0.05 Critical z: 1.96 Population (0 = unlimited): 0
Example result
{
"sampleSize": 385,
"uncorrected": 384.16
}Limitations and details
Uses a normal-approximation planning formula; it does not account for clustering, nonresponse, weighting or a sampling design effect.
Inputs and options
- Expected proportion (0–1)
- Number · Minimum: 0 · Maximum: 1
- Absolute margin (0–1)
- Number · Minimum: 0 · Maximum: 1
- Critical z
- Number · Minimum: 0
- Population (0 = unlimited)
- Number · Minimum: 0
Frequently asked questions
Is this tool free and private?
Yes. All 300 tools are free in this phase. Processing happens in your browser; your input and files are not sent to our servers.