---
title: "Sample Size Calculator — Survey, Research & Clinical Trials"
description: "Calculate required sample size for surveys and research. Enter confidence level, margin of error, and expected proportion. Includes finite population correction. Covers US, UK, AU, EU research standards."
url: "https://worldcalculators.org/calculators/sample-size/"
canonical: "https://worldcalculators.org/calculators/sample-size/"
---

# Sample Size Calculator

Calculate required sample size for surveys and research. Enter confidence level, margin of error, and expected proportion. Includes finite population correction. Covers US, UK, AU, EU research standards.

## Quick answer

Typical surveys: 3–5%

## Frequently Asked Questions

For large populations (N > 10,000), the sample size formula n = (z²pq)/e² is independent of population size. This is counterintuitive but correct: accuracy depends on the absolute sample size, not the proportion of the population sampled. A sample of 400 gives ±5% accuracy whether the population is 10,000 or 1 billion. The finite population correction only makes a meaningful difference when you're sampling more than ~10% of the total population.
YouGov UK typically uses weighted samples of 1,000–2,000 for national surveys (targeting ±3% MoE at 95% CI). Ipsos UK and MORI use similar sizes. US Gallup polls use 1,000–1,500 adults. Australian Essential Media uses 1,000 respondents. All target 95% confidence. The difference from a strict statistical sample is that all these organisations use quota sampling and weighting — not purely random sampling — which affects the effective sample size.

Source: https://worldcalculators.org/calculators/sample-size/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.