Calculate the margin of error for a survey result at a chosen confidence level.
The margin of error depends far more on sample size than on population size. A 1,000-person sample gives roughly the same precision whether the population is fifty thousand or fifty million. That population independence surprises people, but it is why national polls need only about a thousand respondents.
Survey Margin
Margin = z √(p(1−p) ÷ n) × finite population correction
Margin = z √(p(1−p) ÷ n) × finite population correction The margin of error depends far more on sample size than on population size. A 1,000-person sample gives roughly the same precision whether the population is fifty thousand or fifty million.
That population independence surprises people, but it is why national polls need only about a thousand respondents.
This calculator takes 4 inputs: Completed responses, Population size, Observed proportion, Confidence level. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.