Sample Size Calculator
Calculate the required sample size for surveys and research studies with confidence intervals and margin of error
Study Parameters
How confident you want to be in your results
Acceptable range of error in your results
Expected percentage of positive responses (use 50% if unknown)
Formula
n = (Z² × p × (1-p)) / e²
Common Study Types
Results
Set your study parameters and click Calculate to see the required sample size
Sample Size Guidelines
Confidence Levels
90%: Exploratory research
95%: Standard for most studies
99%: High precision required
99.9%: Critical applications
Margin of Error
±1-2%: High precision studies
±3-5%: Standard surveys
±5-10%: Exploratory research
>±10%: Preliminary studies
Best Practices
Use 50% proportion if unknown
Account for non-response rate
Consider practical constraints
Pilot test when possible
Tips
- Enter the dimensions in the same unit for consistency.
- Results update automatically as you type.
- Use the unit selector to convert between different measurement systems.