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Sample size calculator
How many people to survey for a chosen confidence level and margin of error.
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- Works on any device
About Sample size calculator
Works out how many respondents a survey needs for your chosen confidence level and margin of error, using n = z squared x p(1 - p) / e squared. If you do not know the true proportion, 50 percent is the safe assumption. A smaller margin of error needs far more people.
How to use Sample size calculator
- Enter your numbers above.
- The result updates instantly as you type.
- Change any value to compare different cases.
Why use this tool?
- Private: everything happens in your browser. Nothing you enter is uploaded.
- Free, with no sign-up, no watermark and no limit on how often you use it.
- Works on phones, tablets and computers: Android, iPhone, Windows, Mac and Linux. Nothing to install.
- Available in 10 languages.
Also known as
Frequently asked questions
Why does the population size barely matter?
For large populations the needed sample is almost the same, since precision depends on the sample itself. Only when the sample is a big share of a small population does it shrink.
Is Sample size calculator free?
Yes. Sample size calculator on Toolipedia is free to use, with no sign-up and no watermark.
Is it safe to use?
Yes. Everything is worked out in your browser, and nothing you enter is sent to our server.
Does it work on my phone?
Yes. It works in any modern browser on Android and iPhone, as well as on tablets and computers. There's nothing to install.
Do I need an account?
No. Just open the page and use the tool. There's no sign-up and no email needed.