The Bilateral Factor: The 10% Most Veterans Never Hear About

If you've got a rated condition on your right knee and a different rated condition on your left ankle, there's a rule in the VA's math that most veterans have never heard of — and most decision letters don't spell out. It's called the bilateral factor, and it exists specifically because losing function on both sides of your body is more disabling than the raw numbers suggest.

Here's what it is, when it applies, and how to check whether the VA actually gave it to you.

What is the bilateral factor?

The bilateral factor is a rule under 38 CFR § 4.26 that adds a small bonus to your combined rating when you have two or more compensable disabilities affecting paired extremities — both arms, both legs, or paired skeletal muscles.

It's not a separate condition you file for, and it's not a form. It's a step in the VA's combined ratings calculation that's supposed to happen automatically, behind the scenes, whenever the qualifying conditions are present.

What actually counts as "bilateral"?

This is the part that surprises people. The bilateral factor doesn't require the same diagnosis on both sides. It applies whenever compensable disabilities affect the use of paired extremities, regardless of the specific location on each limb.

That means a rated condition on your right thigh and a completely different rated condition on your left foot can both qualify — they don't have to be the same body part or the same diagnosis, just opposite paired limbs.

Common real-world combinations that trigger it:

Radiculopathy is worth calling out specifically: when a rated back or neck condition causes nerve pain radiating down both legs (or both arms), each side is typically rated separately — and together they're a textbook bilateral factor trigger.

How is the bilateral factor calculated?

The calculation happens in three steps, using the same combined ratings table that governs the rest of VA math:

1. Combine your bilateral ratings with each other first, using standard VA math (not simple addition).
2. Add 10% of that combined value on top of it.
3. Treat the result as a single combined bilateral disability, then slot it into your overall order of severity with your other, non-bilateral conditions and combine everything as usual.

A worked example

Say you have four compensable ratings: 60%, 20%, 10%, and 10% — and the two 10% ratings affect paired extremities (say, left knee and right ankle).

1. Combine the two bilateral 10% ratings using VA math: 10% and 10% combine to 19%.
2. Add 10% of that combined value (10% of 19 is 1.9): 19 + 1.9 = 20.9%, which the VA carries forward as 21%.
3. Arrange all values in order of severity: 60%, 21% (the bilateral combined value), and 20%.
4. Combine 60% and 21%: that's 68%.
5. Combine 68% and the remaining 20%: that's 74%.
6. Apply the rounding rule at the very end: 74% rounds down to a 70% final rating.

Without the bilateral factor, that same veteran's 60%, 20%, 10%, and 10% would combine differently and could land on a different final number — sometimes the same tier, sometimes not. The bilateral factor doesn't guarantee a jump, but it's supposed to be in the math every time paired-extremity ratings are present, and skipping it can quietly shortchange a claim.

When would leaving it out actually change my check?

Because the VA only rounds once, at the very end of the whole calculation, whether the bilateral factor changes your final number depends on where the pre-rounding total lands. A few tenths of a percent can be the difference between a 74% that rounds down to 70% and a 75% that rounds up to 80% — which is a full compensation tier, for as long as that rating stands.

Is there an exception?

Yes. If applying the bilateral factor would somehow produce a lower combined rating than leaving the conditions separate, the VA is supposed to skip the bilateral grouping and combine those ratings individually instead — whichever method benefits the veteran is the one that's supposed to be used.

How do I check whether I got it?

Your decision letter typically won't have a line that says "bilateral factor applied." What it will show is your individual condition ratings and your final combined rating. If you have two or more compensable ratings on paired extremities, you can work through the same three steps above using your own numbers and see whether the final combined rating on your letter reflects that extra step, or whether it looks like your ratings were combined without it.

Bottom line

The bilateral factor is a real, automatic part of VA math — not something you request, but something worth checking for. If you have compensable ratings on both legs, both arms, or paired skeletal muscles, walk through the combined ratings table yourself using the steps above. It's a small step in the calculation, but for a veteran sitting right at a rounding line, it can be the difference between two compensation tiers for the rest of a rating's life.

Sources: 38 CFR § 4.26 — bilateral factor, 38 CFR § 4.25 — combined ratings table.