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Sample Size Calculator
How many responses a survey needs.
385
Sample size needed
385
Without population correction
1.96
z
Runs entirely in your browser. Nothing is sent anywhere.
How it works
- 1Enter your values.
- 2See the result update instantly as you type.
- 3Change any value to compare scenarios.
About this tool
Sample Size Calculator: How many responses a survey needs. Type your numbers and the result is calculated instantly — no button to press, nothing to install. All math runs locally in your browser, so the values you enter are never sent anywhere.
Example
| Input | |
|---|---|
| Confidence level | 95 % |
| Margin of error (%) | 5 |
| Expected proportion (%) | 50 |
| Population size (optional) | — |
| Result | |
| Sample size needed | 385 |
| Without population correction | 385 |
| z | 1.96 |
How do I use the Sample Size Calculator?
Enter your values. See the result update instantly as you type. Change any value to compare scenarios.
Is the Sample Size Calculator free?
Yes. It is completely free with no sign-up, no usage limits and no watermark.
Is my data sent to a server?
No. Everything is calculated locally in your browser. Nothing you enter is uploaded, logged or stored.
Does it work on my phone?
Yes. It works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux — no app needed.