Cronbach Alpha Calculator

Work out cronbach alpha instantly with clear inputs, formula shown and shareable results.

About Cronbach Alpha Calculator

Cronbach's alpha measures internal consistency: how far a set of items behave as though measuring one construct. It rises with both the number of items and their average intercorrelation.

Formula

Cronbach's alpha

α = (k/(k−1))·(1 − Σσ²ᵢ / σ²_total)

Worked example

With the default values below, Cronbach Alpha Calculator returns Cronbach's α of 0.83333333. Change any input above and every figure here is recalculated in your browser.

Inputs used

Variance of each item: 1.2, 0.9, 1.5, 1.1, 1.3
Variance of the total scoreminimum 0: 18

Results

Cronbach's α: 0.83333333
Interpretation: Good internal consistency
Number of items: 5
Implied average inter-item correlation: 0.50000000

Step by step

1Values used
2Cronbach's alpha
3Cronbach's α= 0.83333333
4Interpretation= Good internal consistency
5Number of items= 5
6Implied average inter-item correlation= 0.50000000

Assumptions and limits

The result is derived only from the 2 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 8 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

For five items summing to 6.0 variance against a total of 18?

α = (5/4)(1 − 6/18) = 0.8333, which counts as good internal consistency.

Can alpha be too high?

Yes. Above about 0.95 the items are likely redundant, measuring the same narrow thing rather than the broader construct.