Everyday utility

Sample Size Calculator

Determine the required sample size for a survey or study based on population size, confidence level, and margin of error. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
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Calculator tool

How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Sample size formula: n = (Z² × p × (1−p)) / e², where Z is the z-score for confidence level, p is estimated proportion (0.5 for max variance), and e is margin of error. Large populations use finite population correction.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What confidence level should I use?

95% confidence is the most common standard in research. It means if you repeated the survey 100 times, 95 results would fall within your margin of error.