Survey Sample Size Calculator

Know how many responses you actually need. Enter your population, confidence level and margin of error, and this returns the sample size for results you can trust — before you send the survey.

Need more than the free basics? Once you know the number, you need to collect the responses. A survey tool like SurveySparrow runs engaging surveys and gathers the answers for you.

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Confidence and margin of error, explained

Confidence level (usually 95%) is how sure you want to be that the true answer falls within your results; margin of error (often ±5%) is the wiggle room around them. Tighter margins and higher confidence need more responses. Interestingly, beyond a few thousand the required sample barely grows with population — you need surprisingly few people to represent a large group reliably.

Frequently asked questions

How many people do I need to survey?

It depends on your confidence level and margin of error, not just population size. For 95% confidence and ±5%, you often need only a few hundred responses — this tool gives the exact number.

What is margin of error?

The range around your result where the true answer likely sits. A ±5% margin on a 60% result means the real figure is probably between 55% and 65%.

How do I collect the responses?

Send your survey with a tool like SurveySparrow, which runs engaging, conversational surveys and gathers the answers for you.

This tool is free and runs entirely in your browser. The link above is an affiliate link: we may earn a commission if you sign up, at no extra cost to you, and it never changes our honest take.