RESEARCH TOOL

Sample Size Calculator

Estimate the number of people required for a survey using Yamane or Cochran, with every assumption and adjustment shown.

1Choose a method
2Enter your assumptions
3Review and report the result

STEP 1

Choose the appropriate method

If you are unsure, use the guidance below—not whichever formula gives the smaller number.

STEP 2

Enter your study assumptions

Population size OptionalEnter N to apply finite-population correction; otherwise Cochran’s initial estimate is used.Confidence levelHow confident you want to be that the interval captures the population value.Estimated proportion

Use 50% when no reliable prior estimate exists; it gives the most conservative sample.Margin of error

The maximum acceptable difference between the sample estimate and population value. 5% is common.Design effectUse 1.0 for simple random sampling. Enter a larger value for cluster or complex designs when justified.Expected response rate

The percentage of invited participants expected to provide usable responses.

When should I not use this calculator?

Do not rely on these formulas alone for hypothesis tests, regression power, clinical trials, rare outcomes, multistage sampling or studies comparing groups. Those designs require a power analysis or specialist calculation based on the planned analysis.

INTERPRET CAREFULLY

A calculated number is only one part of sampling quality.

Define the population

Specify exactly who is eligible, where they are located and the period covered.

Choose participants properly

A large convenience sample does not replace probability sampling when population inference is required.

Plan for subgroups

If results must be reported separately for groups, ensure each group has enough observations.

Document assumptions

Report the formula, values, adjustment for non-response and the final achieved sample.