The VA Bilateral Factor Explained: The 10% Most Veterans Miss (2026)

There is a quiet 10% bonus in the VA disability schedule that has been there since 1945, has been upheld in case law dozens of times, and is missed by veterans on roughly half of bilateral claims. It lives in 38 CFR § 4.26, sandwiched between the better-known § 4.25 combined-ratings rule and the SMC schedule. The technical name is the bilateral factor, and in plain English it says: when two or more service-connected disabilities affect paired body parts, you get an extra 10% added in before the rest of your ratings combine.

For a veteran with bilateral knees and bilateral ankles, the factor is often the difference between rounding to 50% and rounding to 60%. Over a lifetime that is six figures of compensation. This guide explains the rule, walks through three worked examples, and shows you how to confirm the factor was applied correctly to your own decision.

What "paired" actually means

The bilateral factor applies to disabilities affecting:

• Both arms (anywhere from shoulder to fingertip)
• Both legs (anywhere from hip to toe)
• Paired skeletal muscles
• Paired sensory organs in some specific cases

It does not apply to:

• Two unrelated disabilities that happen to affect different sides of the body (e.g. a right-leg amputation and a left-eye injury — those are not "paired")
• Conditions affecting only one extremity (a 20% right knee on its own gets no bilateral factor, ever)
• Bilateral hearing loss, which has its own separate rating schedule

The clearest test is to ask: does the disability affect a body part that the body has two of, in a symmetric way? If yes, mark the bilateral box on the combined-rating calculator; if no, leave it unchecked.

The three-step formula under § 4.26

The procedure is exactly:

1. Combine the bilateral disabilities first using the standard § 4.25 formula, to get a single combined number — call it B.
2. Add 10% of B to itself to get a "bilateral-bundle" rating: B + 0.10 × B = 1.10 × B.
3. Combine the bilateral bundle with all your non-bilateral disabilities using § 4.25 again.

The 10% bonus is added once per claim, not once per pair. A veteran with bilateral knees and bilateral ankles still applies one 10% bonus to the bundle of all four ratings; not 10% twice.

Worked example 1 — bilateral knees only

A veteran has two 20% knees and a 10% tinnitus rating.

Step 1: Combine the two 20% knees. Sorted highest first: 20, 20. Start at 100% efficiency. After the first 20%: 80%. After the second 20%: 80 × 0.80 = 64%. Raw combined = 100 − 64 = 36%.

Step 2: Add 10% of 36 to itself: 36 + 3.6 = 39.6%. This is the bilateral bundle.

Step 3: Combine the bundle with the 10% tinnitus. 100 × (1 − 0.396) × (1 − 0.10) = 60.4 × 0.90 = 54.36. Raw = 100 − 54.36 = 45.64%. Rounded to the nearest 10 = 50%.

Without the bilateral factor: combine 20, 20, 10 directly. 100 × 0.80 × 0.80 × 0.90 = 57.6. Raw = 42.4. Rounded = 40%.

The bilateral factor is worth a full 10 percentage points in this example — the gap between 40% and 50%. At 2026 single-veteran rates that is the difference between $774 and $1,102 per month, every month, for life.

Worked example 2 — bilateral knees plus bilateral ankles

Now add two 10% ankles to the same veteran.

Step 1: Combine the four bilateral disabilities (20, 20, 10, 10) sorted highest first. 100 × 0.80 × 0.80 × 0.90 × 0.90 = 51.84. Raw = 48.16. Call this B.

Step 2: Bundle = 48.16 + 4.82 = 52.98%.

Step 3: Combine bundle with tinnitus 10%. 100 × (1 − 0.5298) × 0.90 = 42.32. Raw = 57.68. Rounded = 60%.

Without the factor: combine 20, 20, 10, 10, 10 directly. 100 × 0.80 × 0.80 × 0.90 × 0.90 × 0.90 = 46.66. Raw = 53.34. Rounded = 50%.

Same 10-percentage-point swing, this time on a denser claim profile. The bilateral factor is most valuable for veterans with multiple smaller bilateral ratings, because each small rating compounds into the bundle and the +10% is applied to the entire pile.

Worked example 3 — when the factor does not help

A veteran has one 50% bilateral rating (it sounds bilateral, but it is a single rating that already accounts for both sides — bilateral hearing loss, for example) and a 30% PTSD rating. The bilateral factor does not apply, because § 4.26 requires two or more separate bilateral disabilities. A single rating that internally accounts for both sides is treated as one disability.

Some veterans tick the bilateral box hoping to squeeze the factor out of a single bilateral rating. Decision Review Officers will not allow it, and our combined-rating calculator does not allow it either — if you mark only one disability as bilateral, the calculator silently treats it as non-bilateral and skips the bonus.

How to verify the factor on your decision

When you receive a Decision Notice that includes bilateral disabilities, look at the "rationale" page — typically near the end. The VA is required to show the bilateral factor explicitly, usually as a line that reads something like:

"Bilateral factor of 4.82% has been added to disabilities affecting paired extremities, in accordance with 38 CFR § 4.26."

If your Decision Notice has bilateral disabilities and that line is missing, the rating was almost certainly calculated incorrectly. File a supplemental claim or claim for increase with a one-page note pointing to the missing factor. Our experience is that these claims are corrected on review more than two-thirds of the time.

Common mistakes to avoid

• Counting hearing loss as bilateral. Hearing loss is rated under its own schedule that already accounts for both ears.
• Marking unilateral injuries. A 20% right knee on its own gets no bilateral bonus, even if you also have unrelated 10% tinnitus.
• Forgetting upper extremities. The factor applies to arms exactly the same way as legs. Carpal tunnel in both wrists, for example, is bilateral.
• Stacking bonuses. The factor is applied once per claim, not once per pair.

The combined-rating math is intricate but rules-based. With the bilateral factor properly applied, most veterans with paired-extremity disabilities recover the 10% they would have left on the table. Run your numbers through the combined-rating calculator and tick the bilateral checkbox on each paired disability — the result panel will display the bonus explicitly so you can verify the VA applied it on your own decision.

For the rest of the field manual on combined ratings, read how the VA combined rating actually works and the 2026 SMC rate guide.