Margin of Error Calculator

Find the margin of error of a survey from sample size, proportion and confidence level.

Quick answer: Margin of Error Calculator: Find the margin of error of a survey from sample size, proportion and confidence level. Everything runs in your browser, so nothing you enter is uploaded or stored.

Sample size

Proportion (%)

Confidence level

How to use Margin of Error Calculator

Enter your values in the fields.
The results update instantly as you type.
Note or copy the numbers you need.

Features

Instant results
Free, no signup
Runs in your browser, nothing is uploaded
Works on phone and desktop

Formula

MOE = z x sqrt(p(1 - p) / n).

Worked example

With 1,000 respondents at 50 percent and 95 percent confidence the margin is about 3.1 points.

Frequently asked questions

What is the formula?

Margin = z x square root of (p x (1 - p) / n).

What is a typical confidence level?

95 percent, with z = 1.96.

Is the Margin of Error Calculator free?

Yes. It is free, needs no signup and works on any device.