The VA Bilateral Factor Explained: How 38 CFR §4.26 Works

By BilateralFactor Editorial Team · Published June 9, 2026

What the bilateral factor is

VA disability ratings do not simply add up. A 50% rating and a 30% rating do not produce 80%. They combine on the “whole person” efficiency basis to 65%, which rounds to 70%. The bilateral factor is an adjustment on top of that math, applied in one specific situation: when a veteran has partial disability in both arms, both legs, or paired skeletal muscles.

The most common misstatement about the bilateral factor is that it gives you “an extra 10% rating.” It does not. The regulation adds 10% of the already-combined value of your bilateral disabilities, arithmetically, before those disabilities are folded into the rest of your rating calculation. On a 44% combined value, that is 4.4 points, not 10 percentage points. The absolute boost is smaller than many veterans expect, but it is often enough to move the final rating up one full payment step.

The bilateral factor is not a bonus VA chooses to give. It is a mandatory mathematical step under 38 CFR §4.26 whenever the qualifying conditions are present.

Why the bilateral factor exists

Congress and VA recognized that bilateral disabilities impose a compounded burden beyond what simple combined-ratings math captures. When both knees are damaged, the veteran cannot compensate by favoring one side the way a person with a single-knee injury might. The difficulty of daily tasks, employment, and mobility is qualitatively different when the impairment is on both sides simultaneously. The 10% addition is VA’s codified acknowledgment of that compounded impact, built into the rating schedule as a permanent structural element rather than a discretionary enhancement.

This context also explains why the factor applies only to extremities and paired skeletal muscles rather than to every bilateral condition. Internal-organ conditions typically have rating schedules that already account for bilateral severity. The regulation was designed for musculoskeletal and neuromuscular conditions where right-left symmetry directly affects functional capacity.

The exact rule

The regulation reads, in relevant part:

“When a partial disability results from disease or injury of both arms, or of both legs, or of paired skeletal muscles, the ratings for the disabilities of the right and left sides will be combined as provided in §4.25, and 10 per centum of this value will be added (i.e., not combined) before proceeding with further combinations, or converting to degree of disability.”

— 38 CFR §4.26

Three points stand out in that language:

1. “Combined as provided in §4.25”: the bilateral ratings are first combined using the normal efficiency formula (not simply added), in order of severity.
2. “10 per centum of this value will be added (i.e., not combined)”: the word “added” is deliberate. It is simple arithmetic, not another pass through the efficiency table.
3. “Before proceeding with further combinations”: the bilateral group, factor included, becomes a single disability value that then enters the regular severity-order combination with all other disabilities.

The regulation also specifies at §4.26(b) that the factor does not apply unless there is partial disability of compensable degree (meaning 10% or higher) on each of the two paired sides.

When it applies and when it does not

It applies when:

• You have service-connected disabilities rated at 10% or higher in both arms (for example, right elbow arthritis and left shoulder rotator cuff tear).
• You have service-connected disabilities rated at 10% or higher in both legs (for example, right knee meniscus tear and left knee patellofemoral syndrome).
• You have service-connected disabilities of paired skeletal muscles on both sides (for example, bilateral trapezius injuries).

It does not apply when:

• One disability is in an arm and the other is in a leg. The pairing must be arm-with-arm or leg-with-leg.
• Either side has a 0% rating (or is not service-connected). The regulation requires a “compensable degree” on each side, which means at least 10%.
• The condition is not an extremity condition or paired skeletal muscle. A chest, back, or internal-organ disability does not qualify, nor does tinnitus.
• You have a condition in only one extremity with no qualifying counterpart on the other side.

When both pairs qualify (for example, you have bilateral knee conditions and bilateral shoulder conditions) all four extremities combine together into a single bilateral group, and one factor is applied. There is no double-counting with two separate 10% additions. See section 5 below.

The math, step by step

The regulation specifies the order of operations precisely, and 38 CFR §4.25 governs all rounding rules. Here is how the math works in practice.

The §4.25 efficiency formula

Before walking through the bilateral examples, it helps to be clear on the base formula. The §4.25 combined ratings table works on the concept of remaining “whole person” capacity. If you have a 30% disability, you retain 70% of your whole person. A second disability operates on that remaining 70%, not on your original 100%. This is why a 30% and a 20% rating combine to 44%, not 50%:

• 30% disability: 70% remaining.
• 20% of that remaining 70% = 14 additional percentage points of disability.
• 30 + 14 = 44%.

Intermediate values round to the nearest whole number. The final combined value converts to the nearest 10, with values exactly at the midpoint (ending in 5) rounding up.

Example 1: 30% right knee + 20% left knee (bilateral pair only)

1. Sort by severity: 30%, then 20%.
2. Combine using §4.25: 30 + 20 × (100 − 30) / 100 = 30 + 14 = 44. Intermediate values round to the nearest whole number.
3. Apply the bilateral factor: 10% of 44 = 4.4. Add arithmetically: 44 + 4.4 = 48.4, rounded to 48. The bilateral group is now treated as one disability valued at 48%.
4. Convert to final rating: 48 is closest to 50 (rounds to the nearest 10, with values ending in 5 rounding up). Final rating: 50%.

Without the bilateral factor, the combined value would have been 44%, which rounds to 40%. The factor is the difference between a 40% and a 50% final rating.

Example 2: Adding a 20% back condition

Continuing from Example 1, suppose the veteran also has a 20% service-connected lumbar strain (not a bilateral pair; it is a single back condition).

1. Bilateral group value: 48% (calculated above).
2. Sort all disabilities by severity: 48%, then 20%.
3. Combine: 48 + 20 × (100 − 48) / 100 = 48 + 10.4 = 58.4, rounded to 58.
4. Convert to final rating: 58 rounds to 60. Final rating: 60%.

You can verify these calculations and explore your own situation using our VA Combined Ratings Calculator.

Why the factor often crosses a payment threshold

VA compensation rates are tied to the final converted rating, not the raw combined value. The conversion to the nearest 10 creates a 10-point-wide band for each payment level: any combined value from 45 to 54 becomes 50%, any value from 55 to 64 becomes 60%, and so on. Because the factor adds 10 percent of the bilateral combined value, the addition is usually only a few points. Whether those points change your final rating depends on where your total sits within its band.

In the 30%/20% knee example the factor is decisive: 44 alone converts to 40%, while 48 converts to 50%. In other cases it changes nothing. Two 20% leg ratings combine to 36, the factor lifts that to 40 (36 + 3.6, rounded), and both 36 and 40 convert to the same 40% final rating. The only way to know which situation you are in is to run your exact numbers. The calculator shows both the combined value and the final conversion so you can see whether the factor crosses a threshold for you.

Multiple bilateral pairs

When a veteran has qualifying disabilities in all four extremities (for example, bilateral knee conditions and bilateral shoulder conditions) the regulation treats them all as a single bilateral group. All four ratings combine in severity order using §4.25, the 10% factor is applied once to that combined value, and the result enters the remaining combination as one disability.

The regulation provides its own worked example. A veteran has four ratings: 60%, 20%, 10%, and 10%, and the two 10% ratings are the bilateral pair. First, the bilateral pair is handled on its own: 10 and 10 combine to 19, the factor adds 1.9, and 20.9 rounds to 21, which is now treated as a single disability. Second, all values are arranged in severity order (60, 21, 20) and combined under §4.25: 60 and 21 give 68 (68.4, rounded), then 68 and 20 give 74 (74.4, rounded). Finally, 74 converts to a final degree of 70%. The factor is applied only inside the bilateral group, before the group joins the other ratings. It is never applied to the overall total.

The key point: there is never more than one bilateral factor regardless of how many paired extremities are involved. If you have bilateral knee, bilateral hip, and bilateral shoulder conditions all qualifying under §4.26, they all go into one combined calculation and receive one factor adjustment.

How it interacts with combined-ratings order

38 CFR §4.26 specifies that the bilateral group is “converted to degree of disability” and “treated as one disability” for purposes of the remaining combination. In practical terms:

1. Identify all bilateral pairs and combine them (including the factor) into a single value.
2. Place that single value back into the full list of disabilities alongside any non-bilateral conditions.
3. Re-sort the entire list by severity (the bilateral group value may be higher or lower than other conditions).
4. Combine everything in that severity order using §4.25 to reach the final combined value.
5. Convert the final combined value to the nearest 10 using §4.25(a) rounding rules.

This ordering matters. If your bilateral group produces a 48% value and you have other conditions at 30% and 20%, the combination sequence is 48, then 30, then 20, not bilateral last.

Common conditions where the bilateral factor applies

The bilateral factor most often arises with musculoskeletal conditions, because joint and muscle injuries frequently occur on both sides of the body. Common examples include:

Bilateral knee conditions: Meniscal tears, patellofemoral syndrome, chondromalacia, and service-connected arthritis in both knees are among the most frequent bilateral claims. See our detailed breakdown at /conditions/knee/.

Bilateral radiculopathy: When nerve compression from a lumbar or cervical spine condition causes radiating symptoms in both legs (or both arms), each leg (or arm) may carry its own rating, and the pair qualifies for the bilateral factor. See /conditions/radiculopathy/.

Bilateral pes planus (flat feet): Pes planus is rated separately for each foot, and when both feet are service-connected at a compensable degree, the bilateral factor applies. See /conditions/flat-feet/.

Bilateral peripheral neuropathy: Peripheral neuropathy resulting from diabetes, toxic exposure, or other service-connected causes often affects both legs. Each side carries its own Diagnostic Code rating, and the pair qualifies for the factor.

Bilateral shoulder conditions: Rotator cuff tears, labral injuries, and shoulder arthritis on both sides, whether from direct injury or overuse during service, frequently result in bilateral arm ratings.

In all of these situations, the key requirement is the same: service-connected, compensable (10% or higher) ratings on both sides of the same extremity type.

How to check whether VA applied the bilateral factor

Your Rating Decision letter contains the combined rating math VA used to reach your final disability percentage. Look for a section that shows the individual ratings being combined. If you have service-connected conditions in both knees, both arms, or both legs at 10% or higher, you should see:

• A line (or section) where your bilateral disabilities are combined together.
• An explicit addition of the bilateral factor (something like “bilateral factor: +X%”) before the combined bilateral value is folded in with other ratings.

If you do not see that step and you believe you qualify, the most common remedies are:

• Higher-Level Review: if your most recent decision is within one year, a senior reviewer can correct a clear error in how the math was applied.
• Supplemental Claim: if you have additional evidence or the error is older.
• Board of Veterans’ Appeals (BVA) appeal: if you are within the appeal window.

Errors in applying the bilateral factor are not unusual, particularly when the two paired disabilities were rated in different claims or at different times. Keeping your own record of the math and checking it against our VA Combined Ratings Calculator is a practical way to catch these errors early.

If the math in your decision letter does not include the bilateral factor when it should, see what to do after a VA decision you disagree with for the review lanes that can correct a calculation error.

Always consult an accredited VA claims agent, VSO (Veterans Service Organization), or attorney for advice specific to your situation.

Frequently asked questions about the bilateral factor

The four questions below cover the most common points of confusion veterans encounter when researching the bilateral factor. More detail on each is in the FAQ section at the bottom of this page.

Is the factor applied automatically, or do I need to request it? The factor is mandatory by regulation. VA must apply it when the criteria are met without requiring the veteran to ask. Errors do occur, and the most reliable safeguard is checking your own decision letter math.

What if my bilateral condition was rated years before my other paired condition? The factor still applies as long as both conditions are currently service-connected at a compensable degree. A rating from ten years ago on the right knee and a new rating on the left knee both count. If VA rated them separately without applying the factor, a supplemental claim can correct this.

Does the bilateral factor affect my individual ratings? No. The factor does not change the schedular ratings for each condition. A 30% right knee stays 30% and a 20% left knee stays 20%. The factor only affects the mathematical combination: the number that results from putting all the ratings through the §4.25 and §4.26 process.

Can the bilateral factor push me to 100%? The bilateral factor can raise combined values, but the math is constrained by the efficiency formula. Each step combines on the residual basis, so the arithmetic cannot exceed 100%. In practice, the factor adds 10% of the bilateral group’s combined value: roughly 2 points for a minimal 10%/10% pair, up to 9 or so points for severe bilateral ratings. Whether that is enough to reach 100% depends on all the other ratings involved.

Summary

The VA bilateral factor under 38 CFR §4.26 is a required mathematical adjustment that adds 10% of the combined value of qualifying bilateral disabilities before they are folded into the broader rating calculation. It applies to both arms, both legs, or paired skeletal muscles, not to mixed pairs or single-extremity conditions. The factor is added arithmetically, not through the efficiency formula, and the result is treated as a single disability for all further combinations.

Veterans with bilateral knee conditions, bilateral radiculopathy, bilateral pes planus, or bilateral upper-extremity conditions should verify that their Rating Decision reflects this calculation. Use our VA Combined Ratings Calculator to model your own numbers and confirm what your combined rating should be under the regulation.