This guide breaks down the exact formula under 38 C.F.R. § 4.26, shows worked examples, explains which conditions qualify, and explains how to check whether VA applied it correctly in your decision.
The Bilateral Factor Formula
Under 38 C.F.R. § 4.26, when a veteran has service-connected disabilities affecting both arms, both legs, or paired combinations (one arm and one leg), VA must first combine those bilateral conditions together using the whole-person formula, then add 10% of that combined value to the result, and then round to the nearest 10% before continuing to combine with other conditions.
Step 2: Bilateral combined value × 10% = bilateral factor
Step 3: Bilateral combined value + bilateral factor = adjusted bilateral value
Step 4: Round adjusted bilateral value to nearest 10%
Step 5: Use rounded adjusted value in final whole-person combination with all other conditions
The bilateral factor is not optional. VA is required to apply it when the criteria are met. If your decision shows bilateral conditions combined without the factor applied, that is a calculable error in your rating.
Worked Examples
Which Conditions Qualify for the Bilateral Factor
Under 38 C.F.R. § 4.26, the bilateral factor applies when disabilities affect: both arms or both legs (any joints within those extremities), or one arm and one leg. Both conditions must be service connected. The conditions do not need to be the same condition on both sides - a left knee and a right ankle both qualify. The conditions do not need to be at the same disability percentage on both sides.
Conditions that do NOT qualify for the bilateral factor: conditions affecting only one side of the body, conditions affecting the trunk or torso (spine, abdomen), and conditions affecting only organs (heart, lungs, kidneys). Tinnitus does not qualify. PTSD does not qualify (it is not a limb condition). However, if you have PTSD plus bilateral knee conditions, the bilateral factor applies to the knees and the knee result then combines with the PTSD through the standard whole-person formula.
How to Check If VA Applied the Factor Correctly
Your rating decision should show a calculation worksheet. Look for a line showing bilateral conditions combined separately before the main combined rating calculation. If you see your bilateral conditions listed in the same order as all other conditions without a separate bilateral grouping, the factor may not have been applied. Use the ClaimRecon calculator - enter your bilateral conditions first to verify the calculation, then compare it to what your decision shows. If there is a discrepancy, that is the basis for a Higher Level Review arguing clear and unmistakable error in the rating calculation.
- Combined Rating Calculator - applies the bilateral factor automatically when you have paired conditions
- Decision Analyzer - check whether your rating decision applied the bilateral factor correctly
- Secondaries Explorer - find bilateral secondary conditions tied to existing service-connected conditions