Math & Statistics
Sample Size Calculator
Find the sample size needed for a survey at a target margin of error.
Your inputs
Change any value to update the result instantly.
Required sample size
385
Unadjusted sample size
385
Z-score
1.96
Formula and working
n = z²p(1−p) ÷ E²
- 1
Collect the inputs
Expected proportion = 0.5; Desired margin of error = 5 %; Confidence level = 95; Population size (0 = infinite) = 0
- 2
Apply the formula
n = z²p(1−p) ÷ E²
- 3
Result
Required sample size = 385
Frequently asked questions
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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