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sample sizeClassic tool

Sample Size Calculator

Estimate how many responses you need for a survey, poll or study using margin of error and confidence level.

Use this sample size calculator to estimate how many responses you should collect before reviewing a survey, poll, questionnaire or quantitative study. It is useful for marketing, UX research, support analysis, education and any project where you want enough data to make decisions without overspending time or budget.

Enter your target margin of error, confidence level and expected response proportion. If you already know the full population size, you can add it to apply the finite-population correction and get a tighter target. If the population is very large or unknown, simply leave that field blank.

The result gives you a practical minimum response target, the large-population baseline and a quick summary of the assumptions used. That makes it easier to plan recruitment, fieldwork, deadlines and reporting before your survey goes live.

If you do not know the expected proportion, 50% is usually the safest conservative choice.

SummaryThe result updates automatically from the form values.
Recommended sample—
Large-population baseline—
Confidence and margin—
Assumed proportion—
Population—
Applied formulan0 = z² × p × (1 - p) / e²

Use clear inputs to get a more useful result.