Sources & Methodology
Where Our Data Comes From
BilateralFactor draws exclusively on publicly available primary sources. The four sources we rely on are:
- Electronic Code of Federal Regulations (eCFR): all 38 CFR text, including Part 4 (Schedule for Rating Disabilities), §4.25 (combined ratings table), and §4.26 (bilateral factor), is taken directly from ecfr.gov. The eCFR is the authoritative, continuously updated version of the Code of Federal Regulations maintained by the Office of the Federal Register.
- VA.gov: official benefit rate tables, policy announcements, and program descriptions are sourced from va.gov. We link to the specific page, not the homepage.
- M21-1 Adjudication Procedures Manual: VBA's internal adjudication guidance, publicly available via KnowVA, is used where relevant to explain how regulations are applied in practice.
- VBA Annual Benefits Reports: statistical data on veterans, claim volumes, and disability compensation is drawn from VA's publicly released annual reports, available through the VBA reports page.
Source Provenance Rule
Every dataset and article on this site carries a source URL and a retrieval date. The retrieval date records when we last accessed and verified the source. Because regulatory text and benefit rates are updated periodically, the retrieval date tells readers how current our reference was at the time of writing. When a source is updated after publication, we re-verify the article and advance the updated date.
How Rate Tables Are Maintained
The compensation figures on our pay-rate pages and calculators are transcribed from VA.gov's published rate tables in two independent passes that are compared before anything is committed. Each table is stored with its source URL and retrieval date, checked by an automated schema, and covered by tests that fail the build if rates do not rise with rating, if dependents do not add money, or if a new year's table is not higher than the prior year's. Rates are re-verified each December when the cost-of-living adjustment takes effect.
How Calculators Are Tested
The combined rating calculator implements §4.25 and §4.26 directly in TypeScript. The implementation is covered by an automated unit test suite that runs on every code change. The tests include the worked examples from the regulations themselves. If the calculator produces a different result than the example in the regulation, the test fails and the code cannot be deployed.
In addition to the regulation's own examples, the test suite includes edge cases: single-disability inputs, ties where two disabilities share the same rating, inputs that produce combined values ending in exactly 5 (which round up per §4.25), and scenarios with multiple qualifying bilateral pairs. The test suite is maintained in the project repository and is run automatically in continuous integration.
Limitations of Schedular Math
Our calculator and articles describe the schedular combined rating calculation: the mathematical procedure set out in 38 CFR §4.25 and §4.26. This is the standard method VA uses to combine separate disability ratings into one combined rating.
However, an actual VA rating decision involves more than arithmetic. VA adjudicators evaluate the evidence of record, apply diagnostic codes, determine service connection, consider extraschedular ratings, and exercise judgment on ambiguous evidence. Our calculator cannot replicate that process. The number our calculator produces is the schedular math result: what the combined rating would be if all the inputs are correct and no extraschedular considerations apply. It is a reference tool, not a VA decision.
Veterans whose situations involve extraschedular ratings, special monthly compensation, TDIU, or contested service connection should consult an accredited representative who can review their specific evidence of record.