The bilateral factor is one of the least understood parts of VA math, and it is almost always explained using knees. That leaves veterans with hand, wrist, elbow, and shoulder conditions assuming it does not apply to them. It does.
What 38 CFR 4.26 Actually Says
The regulation applies when there are compensable disabilities affecting both upper extremities or both lower extremities. Upper extremity means the entire arm, from shoulder to fingertips. So the factor is triggered by any compensable pairing across your two arms:
- Both hands, for example bilateral carpal tunnel syndrome or bilateral arthritis.
- Both wrists, both elbows, or both shoulders.
- Mixed pairings, such as a right shoulder condition and a left wrist condition. The joints do not have to match. Only the sides do.
It does not apply between an arm and a leg, and it does not apply to the spine, head, or torso.
The Two Requirements People Miss
1. Both sides must be compensable
Compensable means rated 10% or higher. A 0% rating on one side kills the bilateral factor entirely, even though service connection is established. This is why chasing a small increase on your weaker side is often worth far more than the increase itself suggests: moving 0% to 10% adds the rating and unlocks the factor at the same time.
2. It is calculated before everything else
The bilateral group is combined on its own first, the 10% factor is added to that subtotal, and only then does the adjusted number enter your overall combined rating alongside your non-bilateral conditions. Applying the factor at the end produces the wrong answer.
Worked Example: Bilateral Carpal Tunnel
Two wrists, each rated 10% for mild incomplete paralysis of the median nerve.
- Combine the pair: 10% and 10% combine to 19% raw.
- Bilateral factor: 10% of 19 is 1.9.
- Bilateral subtotal: 19 + 1.9 = 20.9%.
- That 20.9% is what enters your overall combined rating.
On its own, 20.9 rounds to 20% and pays $356.66 in 2026 rather than the $180.42 you would get from a single 10%. But the real value shows up when you have other conditions.
Worked Example: Where It Changes the Check
A veteran has PTSD at 50%, plus bilateral carpal tunnel at 10% per wrist. Compare the calculation with and without the factor.
| Without factor | With factor | |
|---|---|---|
| Wrist group | 19.0% | 20.9% |
| Combined with 50% PTSD | 59.5% raw | 60.5% raw |
| Rounded rating | 60% | 60% |
Same tier here. Now shift the PTSD to 60%. Without the factor the raw combined is 67.6, which rounds to 70%. With the factor it is 68.4, still 70%. Move the wrists to 20% each and the picture changes again. The point is not that the factor always moves you up. It is that it is worth roughly one to three raw points, and rating tiers are decided by single raw points at the boundary.
How to Tell If the VA Applied It
Your rating decision letter includes a combined ratings table. If the bilateral factor was applied, the decision narrative will reference 38 CFR 4.26 and show a bilateral factor line in the calculation. If you have compensable ratings on both arms or both legs and there is no such line, the factor was likely omitted. That is a correctable error, and it is worth raising because it costs nothing to ask for a recalculation.
Run your ratings through the bilateral factor calculator →