Interview Sample Saturation Calculator

Work out interview sample saturation instantly with clear inputs, formula shown and shareable results.

About Interview Sample Saturation Calculator

Saturation is judged by the new information rate: new themes from recent interviews as a share of all themes identified. One new theme from the last three out of 32 total is 3.1%, below the 5% threshold Guest and colleagues propose, so saturation is likely reached. Most homogeneous samples saturate between twelve and twenty interviews.

Formulas

New information rate

rate = new themes in the recent base / total themes x 100

Threshold

5% or below is commonly taken as evidence of saturation

Worked example

With the default values below, Interview Sample Saturation Calculator returns New Information Rate of 3.13%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Interviews conductedminimum 1: 18
New themes in the last three interviewsminimum 0: 1
Total themes identifiedminimum 1: 32

Results

New Information Rate: 3.13%
Themes Per Interview: 1.78
Saturation Assessment: Saturation likely reached - two or three confirmatory interviews suffice
Suggested Further Interviews: 3

Step by step

1Values used
2New information rate
3Threshold
4New Information Rate= 3.13
5Themes Per Interview= 1.78
6Saturation Assessment= Saturation likely reached - two or three confirmatory interviews suffice
7Suggested Further Interviews= 3

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How many interviews are usually enough?

Twelve to twenty for a homogeneous sample on a focused question. Heterogeneous samples or broad questions can need fifty or more.

Is saturation a rigorous criterion?

It is the convention but is criticised as unfalsifiable. Reporting the run of interviews with no new themes is more transparent than simply asserting saturation.