About this tool
Find how many survey responses you need for a confidence level and margin of error.
n₀ = z²·p(1 − p) ÷ e² (Cochran). For a known population N it is reduced to n = n₀ ÷ (1 + (n₀ − 1)/N) and rounded up.
Formula: n₀ = z²p(1−p)/e²
Example: Confidence level = 95%, Margin of error = 5, Expected proportion = 50, Population size (0 = very large) = 0 → Sample size for a large population = 384.16, Required sample size = 385.
Assumes a simple random sample. Use 50% when you do not know the expected proportion — it gives the largest sample.
Quick steps
- Enter your values — every field shows its unit.
- Press Calculate (or Try an example to see how it works).
- Read the results and copy them if you need them elsewhere.
The calculation runs in your browser. Nothing you type is sent to 1CLIK.
FAQ
How does the Sample Size Calculator work?
n₀ = z²·p(1 − p) ÷ e² (Cochran). For a known population N it is reduced to n = n₀ ÷ (1 + (n₀ − 1)/N) and rounded up.
What should I keep in mind?
Assumes a simple random sample. Use 50% when you do not know the expected proportion — it gives the largest sample.
Is my data sent anywhere?
No. The numbers stay on your device; the page only shows the result.