Sample Size Calculator
Calculate the required sample size for your survey or research study. Set confidence level, margin of error, and population size to get accurate sample size. Free.
Sample Size Calculator
toolznova.com • Free Calculator
How to Use
Calculate sample size in 3 steps.
Set Population
Enter your total population size (use 1,000,000 for infinite).
Set Confidence & Error
Choose confidence level (95%) and acceptable margin of error (5%).
Get Sample Size
Click Calculate for the required number of respondents.
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Mobile, tablet, desktop.
Why Calculate Sample Size?
- Surveys: Determine minimum respondents for statistically valid survey.
- Research: Academic and market research requires proper sample sizes.
- Quality Control: Inspection sample size for manufacturing batches.
- Clinical Trials: Medical studies need adequate sample sizes for validity.
- A/B Testing: Determine how many users needed for statistically significant test.
- Polls: Election polls and opinion surveys use sample size calculations.
Tips & Examples
- Use p=0.5 when unknown — gives maximum (most conservative) sample size.
- 95% confidence and 5% margin of error is standard for most surveys.
- Larger population doesn't require much larger sample — logarithmic relationship.
- For population 1000: n≈278. For 1,000,000: n≈384 at 95%, 5% margin.
- Doubling precision (half margin of error) quadruples required sample size.
- Response rate < 100% — oversample to ensure enough valid responses.
Free Sample Size Calculator Online
ToolzNova's free sample size calculator determines the minimum number of survey respondents or research subjects needed for statistically significant results at your chosen confidence level and margin of error.
Sample size calculation ensures your research results are statistically valid. Too few respondents leads to unreliable conclusions. This calculator uses the industry-standard formula adjusting for both infinite and finite populations.
Sample Size Formula
n₀ = z²×p×(1-p)/e². Adjusted for finite population: n = n₀/(1+(n₀-1)/N). Where z is the z-score for confidence level, p is expected proportion, e is margin of error, and N is population size.