Survey Sample Size Calculator

How many respondents do you actually need? Enter your parameters below for an instant, statistically sound answer — no signup, no spreadsheet required.

Population size(leave blank for unknown / very large populations)

Confidence level

Margin of error: ±5%

±1% (high precision)±10% (exploratory)

±1%±2%±3%±5%±10%

You need at least

385

respondents for a 95% confidence level with ±5% margin of error (infinite/unknown population)

Uses Cochran's formula with conservative p=0.5 assumption and finite population correction where applicable. Results match SPSS 29 sample-size output.

Quick reference — 95% confidence, ±5% margin

Population	Sample needed
500	218
1,000	278
5,000	357
10,000	370
50,000	382
100,000	383
Unknown / Large	385

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