Cronbach’s Alpha Calculator

What Cronbach’s alpha tells you

Cronbach’s alpha is the most widely reported measure of internal consistency. It shows how closely the items in a scale, such as a five-item satisfaction scale, vary together. A high value suggests the items measure the same underlying construct, which supports the reliability of your questionnaire.

How to interpret the result

• 0.90 and above: excellent, though very high values can mean redundant items.
• 0.80 to 0.89: good.
• 0.70 to 0.79: acceptable for most research.
• 0.60 to 0.69: questionable, often tolerated in exploratory work.
• Below 0.60: poor, so review the scale.

Alpha grows with the number of items, so a long scale can look reliable even when its items are only weakly related. Always read it together with the item-total correlations and the mean inter-item correlation shown above.

How to prepare your data

Put one respondent per row and one item per column. Reverse-code negatively worded items before pasting, otherwise alpha will be too low. Rows with missing values are removed, so impute or clean missing answers first if you want to keep them. Each scale or subscale should be tested separately.

Worked example

The sample data contains 10 respondents who answered five Likert items. Alpha is about 0.94, which is excellent. The table shows that removing any single item would lower alpha, so every item contributes to the scale.