Sample Size Calculator

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

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🧮 Mode

Pick Mean if you know population σ. Pick Proportion for surveys / yes-no outcomes.

🎯 Confidence / Z

Choosing a CL auto-fills z. Selecting “Custom z” lets you type a z-value.

Quick summary

Enter inputs to compute required sample size.

📏 Margin of error (E)

E must be > 0. For proportion, E is absolute (0.03 = 3%).

📐 Population std dev (σ)

Used only in Mean mode.

📊 Estimated proportion (p)

Enter p between 0 and 1. If unknown, use 0.5 (worst-case sample size).

🏷️ Finite population correction

Use when population is not huge relative to sample size.

Required sample size (n)

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We round up to the next whole number.

Base n (before FPC)

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Inputs used

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