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Sample size calculator
Use our sample size calculator to find out how many completed survey responses you need or estimate the margin of error for an existing sample. Results update as you adjust the settings.
White = editable Gray = calculated or inactive
Advanced options
50% gives the largest sample requirement.
1 = simple random sampling; higher values increase variance.
Share of all invitations yielding an eligible, usable completion.
Required completed responses
385
95% confidence · 50% expected percentage · large / unknown population · design effect 1
Margin of error covers sampling uncertainty. It does not account for biased recruitment or unclear questions, and assumes random selection from the population.
For planning surveys that measure percentages, such as awareness, usage or satisfaction.
How this calculator works
Population size - Do you know roughly how many people are in the group you want to study? Enter that number in the sample size calculator to see how many completed survey responses you need. Not sure? Leave it set to “Large or unknown.”
Margin of error - How much “wiggle room” can you accept in your results? This is the margin of error. A common starting point is ±5%: if 50% of your sample chooses an answer, the figure for the whole group could be around 45% to 55%.
Want more precise results? Choose a smaller margin of error, you’ll need more responses. Comfortable with more wiggle room? A larger margin means you need fewer responses. Want results for specific groups, such as age groups or regions? Calculate the sample size for each group separately.
Technical details: The defaults are 95% confidence and an expected percentage of 50%. Margin of error assumes random sampling and does not cover bias in who takes part or how questions are worded. For opt-in or quota samples, use the result as a planning guide.
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