---
title: "Survey Margin of Error Calculator | formformform"
description: "Calculate survey margin of error from sample size, confidence level and population size using finite population correction."
url: "https://www.formformform.com/tools/survey-margin-of-error-calculator"
type: static
generatedAt: "2026-08-23T18:56:58.727Z"
---
# Survey margin of error calculator

Calculate the margin of error achieved by a completed survey sample.

Calculate the margin of error your completed survey actually achieved. Enter the response count, confidence level and, optionally, the population size.

## Starts with uncertainty

The conservative default assumes a 50% proportion, where sampling error is largest.

## Confidence changes the range

Higher confidence uses a larger z-score and therefore a wider interval.

## Finite populations

When a meaningful share of the whole population responds, finite population correction narrows the result.

## Frequently asked questions

What does ±3% mean?

An estimated 50% result would be expected to fall roughly between 47% and 53% at the selected confidence level.

Does this fix sampling bias?

No. It measures random sampling error, not a biased audience or question.

## Other free tools

-   [Survey sample size calculator](https://www.formformform.com/tools/survey-sample-size-calculator)
    
    Work out how many responses you need for a given confidence level and margin of error.
    
-   [Survey response rate calculator](https://www.formformform.com/tools/survey-response-rate-calculator)
    
    Measure delivery, start, completion, response and drop-off rates from a survey funnel.
    
-   [NPS calculator](https://www.formformform.com/tools/nps-calculator)
    
    Calculate Net Promoter Score from pasted 0–10 responses, including the full breakdown.
    

## Want the form to collect the answers too?

Hand-written HTML still needs somewhere to post to. formformform gives you the form, the hosting, the responses and the notifications — free while we are in early access.

[Start free](https://app.formformform.com/register?utm_source=landing&utm_medium=bottom&utm_campaign=tools&utm_content=survey-margin-of-error-calculator)