How to Use the Sample Size Calculator
Before running a survey or poll, it helps to know exactly how many people you need to reach for statistically reliable results. This calculator takes your confidence level, margin of error, expected response rate, and population size, then computes the minimum sample size needed.
If you don't know the expected response rate, entering 50% is the safest choice — it produces the largest possible sample size, guaranteeing your margin of error holds no matter how responses are actually distributed. Population size refers to the total number of people in the group you're studying; leave it blank if it's very large or unknown, and the calculator will assume an infinite population.
Confidence level is the probability that the true value falls within your margin of error if you repeated the same survey many times — 95% is the most commonly used value. Lowering the margin of error or raising the confidence level both increase the required sample size.
Frequently Asked Questions
If you don't know the actual value, enter 50%. This produces the largest — and safest — sample size for any possible response distribution.
No. If the population is very large or unknown, leave it blank and the calculator assumes an infinite population. Entering a small population size gives a more accurate (smaller) sample size.
It's the probability that the true value falls within the margin of error if the survey were repeated many times. 95% is the most common choice.