Split-Half Reliability Calculator
Split a test into two halves, correlate the half scores and step the correlation up to full length with the Spearman-Brown formula. For dichotomous items you also get Kuder-Richardson KR-20 and KR-21.
Updated · By Bibin XavierData 180 × 12
| Respondenttext · 180 levels | TR1numeric · coded | TR2numeric · coded | TR3numeric · coded | TR4numeric · coded | SAT1numeric · coded | SAT2numeric · coded | SAT3numeric · coded | SAT4numeric · coded | LOY1numeric · coded | LOY2numeric · coded | LOY3numeric · coded |
|---|---|---|---|---|---|---|---|---|---|---|---|
| R001 | 2 | 2 | 1 | 2 | 3 | 1 | 3 | 3 | 4 | 2 | 3 |
| R002 | 5 | 4 | 5 | 4 | 3 | 4 | 3 | 4 | 4 | 3 | 4 |
| R003 | 4 | 4 | 3 | 4 | 1 | 2 | 2 | 4 | 2 | 3 | 1 |
| R004 | 1 | 2 | 3 | 2 | 4 | 4 | 4 | 4 | 3 | 4 | 4 |
| R005 | 3 | 4 | 2 | 3 | 3 | 3 | 3 | 4 | 3 | 2 | 2 |
| R006 | 5 | 4 | 5 | 4 | 5 | 5 | 4 | 4 | 4 | 3 | 4 |
| R007 | 3 | 4 | 4 | 4 | 3 | 3 | 2 | 4 | 1 | 3 | 3 |
| R008 | 3 | 3 | 4 | 4 | 5 | 4 | 5 | 5 | 5 | 5 | 4 |
Variables and options
Results
180 rows · example dataSplit-half statistics
| Statistic | Value |
|---|---|
| Part 1 items | TR1, TR3, SAT1, SAT3 |
| Part 2 items | TR2, TR4, SAT2, SAT4 |
| Correlation between forms | .831 |
| Spearman-Brown (equal length) | .908 |
| Guttman split-half (Flanagan-Rulon) | .908 |
| Cronbach’s α (all items) | .850 |
Note. KR-20 and KR-21 are shown only when all items are scored 0/1.
Interpretation
Splitting the 8 items into odd and even halves gives a half-test correlation of .831, which steps up to a full-test reliability of .908 (Spearman-Brown).
How to cite this tool
Using these results in a thesis, journal article, report or class assignment? Please cite this free tool so others can find it. It keeps the site free.
APA 7
Xavier, B. (2026). Split-Half Reliability Calculator [Web application]. FreeStatisticalTools.com. https://freestatisticaltools.com/split-half-reliability-calculator/
BibTeX
@software{xavier_splithalfreliability_2026,
author = {Xavier, Bibin},
title = {Split-Half Reliability Calculator},
publisher = {FreeStatisticalTools.com},
year = {2026},
url = {https://freestatisticaltools.com/split-half-reliability-calculator/},
note = {Web application}
}Suggested sentence for your methods section: “The analysis was carried out with the free Split-Half Reliability Calculator tool on FreeStatisticalTools.com (Xavier, 2026).”
What is split-half reliability?
Split-half reliability divides a test into two halves, correlates the half scores, and uses the Spearman-Brown prophecy formula to estimate the reliability of the full-length test.
When to use split-half reliability
Use split-half reliability for tests given once, especially achievement tests and scales where an odd-even split gives two comparable forms.
How to use this tool
- Enter your data. Paste columns from Excel, Google Sheets or SPSS with variable names in the first row, or upload a CSV or Excel file. The example data shows the expected layout.
- Choose the variables. Select the items.
- Set the options. Fill in how to split.
- Read the results. Results update automatically. Read the plain-English interpretation, then use Copy table to paste APA-style tables into Word and Copy for the results sentence.
How to report split-half reliability in APA style
Report the split method, the correlation between halves and the Spearman-Brown corrected coefficient.
Frequently asked questions
What is the Spearman-Brown formula?
r_full = 2r / (1 + r), where r is the correlation between the two halves.
Odd-even or first-second half?
An odd-even split is usually better because it balances item difficulty, fatigue and content across the halves.
When should I use KR-20?
For tests with dichotomous (right/wrong) items. KR-20 equals Cronbach’s alpha for 0/1 items; KR-21 assumes all items are equally difficult.
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