Cronbach's Alpha Calculator
Paste your item-by-respondent data to compute Cronbach's alpha, item variances, item-total correlations, and a quick interpretation.
Dataset
Rows = respondents, columns = items. Accepts comma, semicolon, tab, or space separation.
| Item | Mean | Variance | Item-total corr. |
|---|
How to Use This Calculator
Paste rows of respondent scores into the textarea. Each column represents an item, so keep every row the same length. The calculator handles commas, semicolons, tabs, or spaces.
Click Calculate to refresh the results. The table updates with each item mean, variance, and item-total correlation.
Methodology
Cronbach's alpha compares the sum of the item variances to the variance of the total score. When items are consistent, the total score variance is higher, yielding a larger alpha.
- The calculator requires at least 2 items and 3 respondents; otherwise the reliability estimate is undefined.
- Item-total correlations are computed by correlating each item with the total score minus that item.
- Variance and covariance use sample (n-1) denominators to maintain alignment with the original implementation.
Interpretation Guide
- ≥ 0.90: excellent internal consistency.
- 0.80 – 0.89: good.
- 0.70 – 0.79: acceptable.
- 0.60 – 0.69: questionable.
- < 0.60: poor — consider revisiting the item set.
Quick Notes
- Ensure all values are numeric (e.g., Likert-type responses between 1 and 5).
- Cronbach's alpha may decrease if you add low-quality items.
- For subscales, run the calculator on each subset of items separately.
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Ugo Candido builds educational tools that make transparent financial and statistical models accessible.
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CalcDomain content is educational, reviewed for clarity, accuracy, and transparency. Inputs and assumptions remain visible so you can verify how results are produced.