Why does sample size matter?

Larger samples provide more precise estimates with smaller margins of error. However, there are diminishing returns - doubling precision requires quadrupling the sample size.

What affects required sample size?

Three main factors: desired margin of error (smaller MOE = larger n), confidence level (higher confidence = larger n), and population variability (higher SD = larger n).

What proportion to use if unknown?

Use 0.5 (50%) as a conservative estimate. This gives the largest possible sample size, ensuring your actual margin of error will be at or below your target.

Do I need to adjust for small populations?

For populations under ~10,000, apply the finite population correction. For larger populations, the correction is negligible and sample size depends only on MOE and confidence.

What is power analysis?

Power analysis determines sample size for hypothesis testing, considering effect size, significance level (α), and desired power (1-β). This calculator focuses on estimation-based sample size.

Sample Size Calculator

Determine the sample size needed for your survey or study.

Estimate Type

Margin of Error (%)

Acceptable margin of error

Expected Proportion (%)

Use 50% if unknown (conservative)

Population Size (optional)

Leave empty for infinite/large population

Confidence Level

Required Sample Size

0

Assuming large/infinite population

Base Sample Size

Z-Critical

MOE

±3%

Sample Size for Different MOEs

±1%

9,604

±2%

2,401

±3%

1,068

±5%

385

Documentation

Sample Size Determination

Sample size calculations ensure your study has enough participants to achieve the desired precision. The formulas differ for estimating proportions vs. means.

Proportion

Mean

FPC

Frequently Asked Questions

How to Use

About the Sample Size

What it calculates

This sample size solves mathematical and statistical problems using standard formulas. Determine required sample size for surveys and studies.

When to use it

Use for homework, data analysis, exam prep, or quick verification of manual calculations.

Example

Adjust the inputs above to model your specific scenario with the Sample Size.

Explore More

Sample Size Calculator

Estimate Type

Confidence Level

0

Sample Size for Different MOEs

Sample Size Determination

About the Sample Size

Related Calculators

Confidence Interval

Margin of Error

Standard Error

ANOVA (One-Way)

Bayes Theorem Calculator

Beta Distribution