Margin of Error Calculator

A poll of 1,000 people has a margin of error of ±3.1% at 95% confidence.

What this calculator does

Doubling sample size reduces margin of error by √2 — not by half.

Frequently asked questions

How do you calculate margin of error?

MoE = z × √(p(1-p)/n). For 95% confidence (z=1.96), 50% response rate, n=1000: ±3.1%.