Cronbach's Alpha Calculator for Survey Scales
Paste item scores to get Cronbach's alpha with a confidence interval, standardised alpha, alpha if item deleted and item-total correlations. Reverse-codes items too.
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What is Cronbach's alpha?
Cronbach's alpha measures the internal consistency of a set of survey items that are meant to measure the same thing, such as a five-statement brand trust scale. If the items move together, alpha is high and you can add them into one score with confidence. It ranges up to 1; values below 0 signal a scoring problem.
How to use the calculator
- Copy the item columns from your data, one respondent per row. A header row with item names is fine.
- List any negatively worded items to reverse-code (e.g. "this brand is a waste of money") and set the scale range.
- Read alpha, its confidence interval and the item analysis.
The data stays in your browser.
Interpreting alpha
| Alpha | Common label |
|---|---|
| 0.9 and above | Excellent (above 0.95 may mean redundant items) |
| 0.8 – 0.9 | Good |
| 0.7 – 0.8 | Acceptable for most research |
| 0.6 – 0.7 | Questionable |
| Below 0.6 | Poor |
These bands are conventions popularised by George and Mallery, not strict rules. Alpha also rises with the number of items, so a long scale can score well even if items are only loosely related.
Using the item analysis
- Corrected item-total correlation: how well each item tracks the rest of the scale. Below 0.3 is weak.
- Alpha if item deleted: if removing an item raises alpha, that item may be measuring something else.
- Negative correlations almost always mean an item needs reverse-coding.
In the example data, the "Value" item correlates weakly with the others; dropping it raises alpha. Press Example to see it.
Frequently asked questions
What is a good Cronbach's alpha?
0.7 or higher is generally acceptable, and 0.8 or higher good. For high-stakes individual decisions, 0.9 or above is often required.
How many respondents are needed?
Alpha can be computed with small samples, but the confidence interval is wide. With 100 or more respondents the estimate is usually stable.
Does a high alpha mean the scale measures one thing?
Not necessarily. Alpha assumes one underlying dimension but doesn't prove it. Use factor analysis to check dimensionality.
Need the respondents, not just the numbers?
Global Vox Populi runs quantitative and qualitative fieldwork in 170+ countries through its own proprietary panels of consumers, B2B and IT decision-makers, physicians, nurses, patients, caregivers and payers. ISO 9001, ISO 20252 and ISO/IEC 27001 certified and HIPAA compliant, following ESOMAR and Insights Association guidelines.
Check feasibilityLink to this tool
Free to use in proposals, courses and articles. If it helped, a link back is appreciated:
<a href="https://globalvoxpopuli.com/tools/cronbachs-alpha-calculator/">Cronbach's Alpha Calculator</a> by Global Vox Populi