Cronbach’s alpha calculator
Paste your data from Excel, Google Sheets or a CSV: one row per person and one column per item, with the scores (for example 1 to 5). If the first row has the question names, it is skipped automatically.
The calculation runs in your browser. We don’t store what you type.
How it’s calculated
α = k / (k − 1) × (1 − Σ item variances / variance of the total score), where k is the number of items.
It uses the sample variance (divided by n − 1), the same as SPSS and most methods textbooks.
“Alpha if item deleted” repeats the calculation without each question. If it rises a lot when one is removed, that question isn’t measuring the same thing as the rest.
How to read the result
- Common scale (George and Mallery): 0.9 or more excellent, 0.8 good, 0.7 acceptable, 0.6 questionable, 0.5 poor and below 0.5 unacceptable.
- Calculate one alpha per dimension or scale in your questionnaire, not one for all questions together.
- A very high alpha (above 0.95) can mean repeated questions that say the same thing in different words.
- If a question is reverse-worded (for example “I get bored in class”), reverse its scores before pasting.
Frequently asked questions
- How many people do I need for the pilot test?
- Usually 20 to 30 people similar to your final sample. With fewer than 10, alpha is very unstable.
- Does it match SPSS?
- Yes. It uses the same formula and the same sample variance, so the result matches SPSS’s Reliability Analysis.
- Does it work for yes/no questions?
- For dichotomous items (0 and 1), alpha is equivalent to KR-20, so you can use it too.
Know what you want to ask?
Build the survey in SurvIQ, share it by link, WhatsApp or QR code, and watch results come in live. The Free plan is free forever.
Create a free survey