Margin of Error Calculator
Shows how far a survey percentage could reasonably be from the true figure, by sampling chance.
Margin of error
— points
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Lower bound — %
Upper bound — %
z used —
Reading this —
The formula
margin = z × √(p(1 − p) ÷ n) × √((N − n) ÷ (N − 1))
The last factor is the finite population correction, used only when you enter a population size.
What to watch out for
The margin depends on the square root of the sample size, so halving it takes four times the sample.
Frequently Asked Questions
What is the margin of error for 1,000 responses?
At most 3.1 percentage points at 95% confidence.
Does population size matter?
Rarely. A sample of 1,000 from a population of 10,000 gives 2.94 points, and from a far larger one 3.1.