What Is Sample Size?
The number of respondents a survey needs for its results to reliably represent the larger population being studied.
Sample size is how many completed responses you need before you can trust the results as representative of a bigger group — all your employees, all your customers, a target market — rather than just an opinion from whoever happened to answer.
Required sample size is driven by three things: how large the total population is, how tight a margin of error you’re willing to accept, and how confident you want to be in the result (typically expressed as a 95% or 99% confidence level). Counterintuitively, once a population gets large enough (a few tens of thousands and up), the required sample size barely grows any further — surveying a population of 50,000 and a population of 5 million require a very similar sample size for the same margin of error.
Undersized samples produce results that swing wildly on small changes in who happened to respond; oversized samples cost more time and incentive budget without meaningfully tightening the result. The right size is the smallest one that gets you the margin of error and confidence level your decision actually needs.
Example
For a large population, roughly 385 responses gets you a 95% confidence level with a ±5% margin of error — the most common "good enough for most business decisions" target.
How to Calculate Sample Size for SurveyRock
Use SurveyRock's free sample size calculator to work out exactly how many responses you need for your population, margin of error, and confidence level before you launch.
Use the sample size calculator