VA CLAIMS EDUCATION · APRIL 2026
VA Math and the Bilateral Factor in 2026 — How the Calculation Actually Works
The bilateral factor is one of the most misunderstood rules in VA disability math — and one of the most commonly missed. If you have service-connected conditions affecting paired extremities (both arms, both legs, or combinations), VA is required to apply an additional factor to your combined bilateral rating before computing your final percentage. Use the ClaimRecon combined rating calculator to run the exact math on your specific conditions, and the secondaries explorer to check whether your bilateral conditions have secondary connections.
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.
THE FORMULA
Step 1: Combine all bilateral conditions using whole-person method
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
Both knees rated 20% each
STEP 1Combine bilaterals: 20% + (20% × 80%) = 36%
STEP 2Bilateral factor: 36% × 10% = 3.6
STEP 3Add factor: 36% + 3.6% = 39.6% → rounds to 40%
WITH BILATERAL FACTOR: 40%
Left knee 30%, right knee 20%
STEP 1Combine bilaterals: 30% + (20% × 70%) = 44%
STEP 2Bilateral factor: 44% × 10% = 4.4
STEP 3Add factor: 44% + 4.4% = 48.4% → rounds to 50%
WITH BILATERAL FACTOR: 50%
Both shoulders 30% + existing 50% PTSD
STEP 1Combine bilateral shoulders: 30% + (30% × 70%) = 51%
STEP 2Bilateral factor: 51% × 10% = 5.1 → combined bilateral = 56.1%
STEP 3Combine with PTSD: 56.1% enters whole-person calculation first
WITH BILATERAL FACTOR: Significantly higher combined rating
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.
Frequently Asked Questions
Does the bilateral factor apply to conditions rated at 0%?
A 0% service-connected condition does not contribute to the combined rating calculation and therefore does not trigger the bilateral factor. The bilateral factor only applies when at least one of the bilateral conditions is rated above 0%. However, a 0% service-connected condition on one side does not prevent you from claiming the bilateral factor for a future rating increase on that same condition.
Can I get the bilateral factor if my conditions are rated under different diagnostic codes?
Yes. The bilateral factor is based on anatomical location (paired extremities), not on diagnostic codes. A left knee rated under DC 5260 (limitation of flexion) and a right knee rated under DC 5003 (degenerative arthritis) both qualify for bilateral factor consideration because they affect paired extremities.
Does filing a bilateral condition claim at the same time as a primary claim matter?
Filing both conditions in the same claim does not affect whether the bilateral factor is applied — it depends on whether both conditions are service connected. However, filing both at the same time protects your effective date for both conditions simultaneously, which maximizes retroactive pay if both are granted.
What if I only have one service-connected limb condition but develop a related secondary on the other side?
A secondary condition under 38 C.F.R. § 3.310 that affects the paired extremity — such as hip arthritis secondary to an altered gait from a service-connected knee — qualifies for bilateral factor calculation once it is service connected. Filing the secondary claim as early as possible protects the effective date and brings the bilateral factor into play sooner.
Educational tools only — not legal or medical advice. Consult an accredited representative for your specific situation. Not affiliated with the U.S. Department of Veterans Affairs. ClaimRecon LLC.