Sample Size Calculator
Enter your population size, confidence level, and margin of error to instantly calculate the minimum sample size needed for a statistically valid survey.
Study Parameters
Total number of people in the group you are studying. Use 1,000,000 if unknown or very large.
How certain you need to be that your results reflect the true population value.
Acceptable range of error. Smaller values require larger samples.
%
Expected share answering "yes". Use 50% for the most conservative (largest) sample.
%
Required Sample Size
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responses needed
Quick Presets
Summary
Enter your population size, confidence level, and margin of error to instantly calculate the minimum sample size needed for a statistically valid survey.
How it works
- Enter your total population size (or leave at 1,000,000 for large or unknown populations).
- Select a confidence level — 95% is the most common choice for surveys.
- Set your desired margin of error (e.g., ±5% means results are accurate within 5 percentage points).
- Optionally adjust the expected response proportion (default 50% gives the most conservative, largest sample).
- The calculator applies the standard formula and finite population correction, then rounds up to give the minimum required sample size.
Use cases
- Plan the number of survey responses needed before launching a customer satisfaction study.
- Determine how many product testers are required for statistically meaningful A/B test results.
- Size a market research project to justify a budget request.
- Validate that an existing dataset is large enough to draw reliable conclusions.
- Academic researchers planning experiments requiring a specific confidence level.
- Political polling — estimate how many voters to interview for a ±3% margin of error.
- Quality control teams calculating inspection sample sizes from production batches.
- Healthcare studies sizing patient cohorts for clinical significance.
Frequently Asked Questions
Last updated: 2026-06-10 ·
Reviewed by Nham Vu