š Sample Size Calculator
Determine the minimum sample size needed for a survey or study to achieve a given confidence level and margin of error.
Study Parameters
Your Result
This is the minimum number of respondents needed to be confident your results reflect the full population within the stated margin of error.
How the Sample Size Calculator Works
Sample size calculations tell you how many people you need to survey to get statistically reliable results. The calculation depends on how confident you want to be (confidence level), how much error you can tolerate (margin of error), and how variable the responses are expected to be (proportion).
Formula
With finite population correction: n = nā / (1 + (nā ā 1) / N)
z = z-score for confidence level, p = expected proportion (decimal),
e = margin of error (decimal), N = population size
Frequently Asked Questions
What proportion value should I use?
If you don't know the expected proportion, use 50% ā this is the most conservative estimate and produces the largest (safest) sample size.
Do I need to enter a population size?
Only if your population is small and known (e.g. surveying 500 employees). For large or unknown populations, leave it blank and the calculator treats the population as effectively infinite.
What confidence level should I choose?
95% is the most common choice for surveys and research, balancing reliability with a reasonable sample size. Use 99% for higher-stakes studies where more certainty is required.