Margin of Error Calculator
For surveys & polls. Uses the standard normal approximation for proportions.
Margin of Error
± 9.80%
MOE = Z × √(p(1−p) / n)
How It Works
The margin of error tells you how much survey results may differ from the true population value.
MOE = Z × √( p(1 − p) / n )
- Z — Z-score for your confidence level (e.g. 1.96 for 95%)
- p — expected proportion (use 0.5 for maximum/worst-case MOE)
- n — sample size
If you know the total population size N, a finite population correction (FPC) is applied:
MOE = Z × √( p(1 − p) / n ) × √( (N − n) / (N − 1) )
Common Z-Scores
1.645
90% confidence
1.960
95% confidence
2.326
98% confidence
2.576
99% confidence