Survey sample size calculator
How many responses you need, and how many people to invite to get them.
Leave empty if it's a large or unknown audience.
Your own past rate is the best guess.
How many survey responses do you need?
The short answer: To report a percentage within 5 points at 95% confidence, you need about 385 responses. A small audience needs fewer, and a tighter margin needs more. If you only want to hear what people say in their own words, a few dozen written answers usually show the main things.
It uses the standard formula for a percentage, n = z² × p × (1 − p) ÷ e², with p = 0.5 (the safest guess), then corrects for a small audience when you give one. Nothing you type leaves your browser.
FAQ
How many survey responses do I need?
To report a percentage within 5 points at 95% confidence, about 385. That comes from n = z² × p × (1 − p) ÷ e² with z = 1.96, p = 0.5 and e = 0.05, which gives 384.16, rounded up.
Does a small audience need fewer responses?
Yes. When your whole audience is small, the finite population correction lowers the number. For an audience of 500 at 95% confidence and a 5-point margin, you need about 218 responses.
What margin of error should I use?
Five points is the usual choice for a percentage you plan to report. Use 3 points if small differences matter to the decision, and 10 points if you only need a rough read.
How many people should I invite?
Divide the responses you need by the share of people you expect to answer. If you need 385 responses and expect 1 in 5 to reply, invite about 1,925 people. Use your own past response rate if you have one.
Do I need this many responses for open-ended questions?
No. This number is for measuring a percentage. If you want to hear what people say in their own words, a few dozen written answers usually show you the main things people say.