Free tool
Survey sample size calculator
Work out how many survey responses you need, and how many people to invite, with the formula and a sentence you can adapt for your methodology chapter.
Use 50% if you do not know the expected proportion; it gives the safest (largest) size. For comparing groups or regression, also run a power analysis.
What sample size do I need for a questionnaire?
For estimating a percentage with a 5% margin of error at 95% confidence, about 385 responses are needed for a large population, fewer for small populations. Your design, analysis and guidelines may change this.
Which formula does this calculator use?
Cochran's formula n₀ = Z²·p(1−p)/e², with the finite population correction n = n₀ / (1 + (n₀ − 1)/N) when you enter a population size.
Is this enough for regression or comparing groups?
Not always. Hypothesis tests need a power analysis based on the expected effect size, for example using G*Power. Ask your guide which approach your study needs.
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