Margin of Error Calculator

Mean • Proportion • Confidence level • Ajax loading • Hard reset

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🧮 Mode

Pick Mean when you know population std dev (σ). Pick Proportion for surveys/yes-no outcomes.

🎯 Confidence / Z

If you choose a confidence level, z auto-fills. Choose “Custom z” to type your own.

Quick summary

Enter inputs to compute margin of error.

👥 Sample size (n)

Must be a positive number.

📏 Population std dev (σ)

Used only in Mean mode.

📊 Estimated proportion (p)

Enter p between 0 and 1. If unknown, use 0.5 for “worst-case” MoE.

Margin of error

—

MoE in the same units as σ (Mean) or as a proportion (Proportion).

As percentage

—%

Useful for survey results.

z used

—

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