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
Work out how many responses you need for a given confidence level and margin of error.
- Survey response rate calculator
Measure delivery, start, completion, response and drop-off rates from a survey funnel.
- NPS calculator
Calculate Net Promoter Score from pasted 0–10 responses, including the full breakdown.
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