Sample Size Estimator
Estimate the survey sample size needed for a margin of error and confidence level, with finite population correction and response rate.
Your inputs
Results
Completed responses needed
385
- People to invite at your response rate
- 385
- Before finite population correction
- 384.15
≈Estimate based on the stated model and assumptions
What this calculator does
Plan how many responses a survey needs to reach a given margin of error and confidence level, and how many people to invite once you account for non-response.
Formula and method
Worked example
Calculated by this tool with its default inputs:
Inputs
- Confidence level: 95 %
- Margin of error: 5 %
- Expected proportion: 50 %
- Population size (optional):
- Expected response rate: 100 %
Results
- Completed responses needed: 385
- People to invite at your response rate: 385
- Before finite population correction: 384.15
How to read the results
About 385 responses give ±5 % at 95 % confidence for a large population.
Assumptions and limitations
- Assumes simple random sampling.
Questions
Why does population size matter so little?
For large populations, precision depends on the sample size, not the share of the population sampled.
Methodology and verification
- Result type
- Estimate based on the stated model and assumptions
- Formula version
- 1.0
- Automated verification
- 4 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy