Calculate the required sample size for your survey with confidence intervals and margin of error. Perfect for market research, healthcare surveys, and academic studies.
Enter your research parameters below to determine the statistically valid sample size for your survey.
Fill in your confidence level, margin of error, and population size to calculate the required sample size.
The sample size formula uses the Z-score for your confidence level, the proportion (50% for maximum variability), and your margin of error:
Where: Z = Z-score, p = proportion (0.5), E = margin of error
Get our free guide with sample size tables, formulas, and best practices for healthcare market research.
A good sample size depends on your research goals, desired confidence level, and acceptable margin of error. For most surveys, a 95% confidence level with a 5% margin of error is considered standard.
How to calculate sample size for a survey?
Use our free sample size calculator above. Enter your confidence level (typically 95%), margin of error (commonly 5%), and population size to get your required sample size.
What is the formula for sample size?
The sample size formula is: n = (Z² × p × (1-p)) / E², where Z is the Z-score, p is the population proportion (0.5 for maximum variability), and E is the margin of error.
What sample size do I need for a 95% confidence level?
For a 95% confidence level with a 5% margin of error, you need 385 respondents for a large population. Use our calculator above to adjust for different confidence levels and margins of error.
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