Common survey
95%, 5% margin, 50% proportion385
Sample Size Calculator
Use this free sample size calculator to estimate a survey sample size from confidence level, margin of error, estimated proportion, and optional population size.
Inputs to check Example numbers Copyable answer Tab-only history
Required sample size385
- Z-score
- 1.96
- Raw n
- 384.16
- Adjusted n
- n/a
How to use the Sample Size Calculator
- Choose a confidence level such as 90%, 95%, or 99%.
- Enter the margin of error and estimated population proportion as percentages.
- Add a finite population size only when you know the population is limited.
- Press Calculate sample size to see the required sample and formula steps.
What people use it for
Estimate how many survey responses you need for a proportion.
Compare 90%, 95%, 98%, and 99% confidence levels.
Use 50% estimated proportion for a conservative planning estimate.
Apply finite population correction when the total population is known.
Quick examples
Finite population
95%, 5%, 50%, population 1,000278
Higher confidence
99%, 5%, 50%664
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Sample Size Calculator See slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- Calculators Browse related calculators and utilities in the same category.
- Calculator and utility guides Find more guides that use real tool inputs and example numbers.
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Frequently asked questions
Quick answers about formulas, inputs, examples, result copying, and private in-browser history.
What kind of sample size does this calculator estimate?
It estimates sample size for a population proportion, which is common for surveys, polls, yes/no questions, and percentage estimates.
What should I enter for population proportion?
Use your best estimate. If you are unsure, use 50%, which gives the most conservative and usually largest sample size.
What do the main Sample Size Calculator inputs mean?
The main inputs are the numbers, operation, mode, or known values the calculator needs. Keep units consistent, enter percentages the way the page label shows, and use the examples as a quick check before trusting the answer.
How should I read the Sample Size Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the Sample Size Calculator?
Check units, signs, rounding, and the selected mode before copying the answer. If the number feels weird, rerun one of the examples first, then put your own values back in slowly.
What is margin of error?
Margin of error is the maximum difference you are planning to tolerate between the sample estimate and the true population proportion.
What does finite population correction do?
When the total population is known, finite population correction can reduce the required sample size because the sample is a larger share of the whole group.
Can this replace professional survey design?
No. It is a planning calculator for common proportion estimates. Professional surveys may need design effects, stratification, weighting, and nonresponse planning.
Is my sample size history private?
Yes. Recent sample size answers stay only in the current browser tab while you use the page. They are not sent to a server.
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