The bilateral factor is one of the most overlooked rules in VA disability — an automatic 10% boost when disabilities affect paired parts of your body. It can be the difference between two rating levels, and many veterans never realize they qualify.
What the bilateral factor is
Under 38 CFR §4.26, when you have compensable disabilities affecting both arms, both legs, or paired skeletal muscles, the VA combines those paired disabilities first and then adds 10% of the combined value before working them into the rest of your rating.
The idea: losing function on both sides of the body is more disabling than the same losses on one side. Two bad knees limit you more than one bad knee and one bad shoulder, so the regulation rewards the bilateral pattern.
How it's calculated
The bilateral factor is applied in a specific order:
- Combine the bilateral disabilities together using normal VA math.
- Add 10% of that combined value (this is the bilateral factor).
- Combine the result with your remaining, non-bilateral ratings.
- Round the final total to the nearest 10%.
Worked example
Say you have a 40% right knee and a 20% left knee — a classic bilateral pair — plus a 30% back condition.
- Combine the two knees: 40 combined with 20 = 52.
- Add the 10% bilateral factor: 52 + 5.2 = 57.2, rounded to 57.
- Now combine 57 with the 30% back: 57 + (30% of the remaining 43) = 57 + 12.9 = 69.9 → 70.
- Final rating: 70%.
Without the bilateral factor, those same three ratings (40, 30, 20) combine to a 66 value — which still rounds to 70%, but with much less cushion. In many real cases the extra 10% is what pushes a veteran from, say, 60% to 70%.
Why it's so easy to miss
The bilateral factor is applied automatically by the VA when the conditions qualify — but only if the disabilities are correctly identified as bilateral in your rating decision. If a knee was rated without noting the other knee, or a hand condition wasn't paired with the matching one, the factor can be left out. Reviewing your rating decision for paired conditions is one of the simplest ways to find money you may be owed.
What counts as "paired"
- Yes: right knee + left knee; right wrist + left wrist; right foot + left foot; bilateral hearing-related muscle/limb groups.
- No: one knee + lower back (back isn't a paired extremity); right knee + right ankle (same side); tinnitus + a single shoulder.
When in doubt, leave the box unchecked in the calculator — that gives you the conservative (lower) estimate. If you think you qualify, an accredited VSO or claims representative can confirm whether your conditions meet §4.26.