The VA Math Rule Most Veterans Never See

If you have compensable disabilities affecting both arms, both legs, or paired skeletal muscles, VA may calculate part of your combined disability rating differently.

This is called the bilateral factor.

The bilateral factor does not simply add 10 percentage points to your overall VA rating. Instead, VA first combines the qualifying disabilities affecting both sides of the body and then adds 10% of that combined value before continuing the rest of the VA-math calculation.

That distinction matters.

The bilateral factor may increase the raw number behind your combined rating, but it does not always change the final percentage rounded to the nearest 10%.

This guide explains when the bilateral factor may apply, how the calculation works, and how to check whether it appears to have been considered.

What Is the VA Bilateral Factor?

The bilateral factor is a special calculation used for certain compensable disabilities affecting paired extremities or paired skeletal muscles.

Under 38 C.F.R. § 4.26, when qualifying disabilities affect both arms, both legs, or paired skeletal muscles, VA generally:

1. Combines the qualifying right- and left-side disability ratings.
2. Calculates 10% of that combined value.
3. Adds that amount to the combined bilateral value.
4. Treats the resulting bilateral value as one disability.
5. Continues combining it with any other service-connected disabilities.

The extra amount is 10% of the bilateral combined value—not 10% added directly to the veteran’s final disability rating.

Why Does the Bilateral Factor Exist?

A disability affecting one leg can limit walking, standing, lifting, or balance.

When disabilities affect both legs, the veteran may not have a stronger unaffected leg available to compensate. The same general problem may occur when compensable disabilities affect both upper extremities.

The bilateral-factor rule recognizes the additional functional impact that can result when both sides of a paired body system are impaired.

The rule applies to ratings and calculations. It does not automatically establish that a condition is related to military service.

Each disability must still be properly service connected and evaluated.

Which Disabilities May Qualify?

The rule potentially applies when there is a compensable disability affecting each of two paired extremities or paired skeletal muscles.

Examples may include compensable disabilities involving:

• The right and left knees
• The right and left ankles
• The right and left feet
• The right and left hips
• The right and left shoulders
• The right and left elbows
• The right and left wrists
• The right and left hands
• Nerve conditions affecting both lower extremities
• Nerve conditions affecting both upper extremities
• A qualifying condition in one part of an extremity and another qualifying condition in the opposite paired extremity

The disabilities do not necessarily have to affect the exact same joint.

The regulation explains that “arms” and “legs” refer to the extremities as a whole. For example, a compensable right-thigh disability and a compensable left-foot disability may potentially be included in the bilateral calculation.

Do the Conditions Have to Be the Same?

No.

A veteran does not necessarily need the same diagnosis or diagnostic code on each side.

The central issue is whether the veteran has qualifying compensable disabilities affecting paired extremities or paired skeletal muscles.

Possible examples include:

• Right-knee limitation and left-ankle limitation
• Right-hip disability and left-knee disability
• Right-leg radiculopathy and left-leg radiculopathy
• Right-shoulder disability and left-wrist disability

That does not mean every condition involving two sides of the body automatically qualifies. VA must determine whether the particular disabilities fall within the bilateral-factor rule.

Do Both Disabilities Have to Be Compensable?

Generally, yes.

The current regulation states that the bilateral factor is not applicable unless there is a partial disability of compensable degree in each of two paired extremities or paired skeletal muscles.

A condition evaluated at 0% is service connected but is not ordinarily a compensable evaluation.

Therefore, a 10% right-knee disability combined with a 0% left-knee disability would not ordinarily satisfy the requirement for compensable disabilities on both sides.

Always review the actual rating decision and applicable diagnostic codes rather than assuming that every bilateral diagnosis receives the factor.

How Is the Bilateral Factor Calculated?

VA does not add ordinary disability ratings together.

Under 38 C.F.R. § 4.25, VA applies its combined-ratings method in order of severity, starting with the highest evaluation.

For bilateral disabilities, the qualifying right- and left-side ratings are handled first.

Simple example: 20% and 10%

Assume a veteran has:

• 20% for a right-leg disability
• 10% for a left-leg disability

Using VA’s combined-ratings table:

• 20% combined with 10% produces 28%.
• Ten percent of 28 is 2.8.
• VA adds the 2.8 to 28.
• The bilateral value is therefore approximately 30.8 before it is used in the remaining calculation.

The veteran has not received an extra 10 percentage points. The bilateral adjustment in this example is 2.8 points.

If the veteran has other service-connected disabilities, the adjusted bilateral value is then combined with those remaining evaluations in the required order.

Another example: 20% for each leg

Assume a veteran has:

• 20% for a right-leg disability
• 20% for a left-leg disability

Using VA’s table:

• 20% and 20% combine to 36%.
• Ten percent of 36 is 3.6.
• The bilateral value becomes approximately 39.6 before further combinations.

If these are the veteran’s only two disabilities, normal final-rounding rules still apply. If the veteran has other ratings, the adjusted bilateral value is combined with those other evaluations.

Why Doesn’t VA Just Add the Ratings?

VA math is based on what the regulations describe as the veteran’s remaining efficiency.

A veteran rated at 50% is treated as having 50% remaining efficiency. A second 30% rating is applied to that remaining portion rather than simply added to the original 50%.

The result of 50% combined with 30% is 65%, which is then rounded to a final 70% if those are the only ratings involved.

This is why:

• 50% plus 30% does not equal 80%
• Two 50% ratings do not equal 100%
• Several smaller ratings may not move the final rounded percentage
• A bilateral factor can affect the raw combined value without changing the final rounded rating

Use the free Informed Veteran VA Disability Rating Calculator to test different combinations and see how VA math affects the estimated final percentage.

The calculator is educational and should not replace the calculation shown in an official rating decision.

Can the Bilateral Factor Apply to Four Extremities?

Yes.

If a veteran has qualifying compensable disabilities involving both upper extremities and both lower extremities, the regulation provides a process for combining the affected extremity ratings and applying the bilateral factor.

The calculations can become difficult when a veteran has:

• Multiple ratings in the same extremity
• Separate nerve ratings
• Disabilities in all four extremities
• Additional non-bilateral ratings
• A combination approaching 100%

In those situations, it is especially important to review the code sheet or rating breakdown rather than relying only on the rounded number displayed in a benefits summary.

Can Applying the Bilateral Factor Ever Produce a Worse Result?

The regulation contains an important exception.

Since April 2023, 38 C.F.R. § 4.26(d) has directed VA to remove one or more disabilities from the bilateral calculation when including them would produce a lower combined evaluation than calculating them separately.

In other words, the calculation should be arranged to produce the evaluation most favorable to the veteran when this exception applies.

This situation is uncommon, but it can happen because of the order in which disabilities are combined and the rounding used in VA math.

Does “Bilateral” in a Diagnostic Code Always Mean the Bilateral Factor Applies?

Not necessarily.

Two different concepts can use similar language:

1. A diagnostic code may provide a particular evaluation for a bilateral medical condition.
2. The separate bilateral-factor calculation may apply under § 4.26.

These are not always the same thing.

For example, a rating schedule may already evaluate a particular bilateral condition under one diagnostic code. Whether the separate bilateral factor also applies depends on the rating structure and the specific disabilities involved.

Avoid assuming that the word “bilateral” in a diagnosis automatically means an additional 10% calculation must appear.

How Can You Check Whether VA Applied the Bilateral Factor?

Your general benefits letter may show only the final rounded percentage. It may not provide every step of the calculation.

Review:

• Your rating decision
• The list of service-connected disabilities
• The percentage assigned to each condition
• The effective date of each rating
• The diagnostic codes
• Any available rating code sheet
• The combined evaluation shown for each period

Then identify whether you have compensable disabilities affecting:

• Both lower extremities
• Both upper extremities
• Paired skeletal muscles

Enter the ratings into the free VA Disability Rating Calculator and compare the estimate with the combined evaluation in your decision.

Remember that an online calculator may not capture every unusual rating scenario. Differences may also result from:

• Effective dates
• Staged ratings
• Temporary ratings
• Ratings that were not effective during the same period
• Conditions VA did not include in the bilateral group
• Special rating rules
• Rounding order
• A calculation error in the online tool

If the numbers still do not make sense, consider discussing the decision with an accredited VSO, accredited claims agent, or veterans-law attorney.

What If You Think the Bilateral Factor Was Missed?

Do not immediately file a new disability claim just because the combined number appears incorrect.

First:

1. Confirm that both disabilities were service connected during the same period.
2. Confirm that each side had a compensable evaluation.
3. Verify that the disabilities involve paired extremities or paired skeletal muscles.
4. Recreate the calculation using the ratings and effective dates shown in the decision.
5. Review whether the final rounded rating would actually change.
6. Read the decision-review deadline and options stated in your VA decision letter.

If you disagree with a recent decision, start with the Informed Veteran guide to VA denials and appeals.

The proper review option depends on the specific error, the evidence available, and the date of the decision.

How This Fits Into a Larger Rating Strategy

Correct VA math is only one part of evaluating a disability rating.

If you believe your overall rating does not reflect your disabilities, review all five possible paths:

1. Existing service-connected conditions that have worsened or may have been underrated
2. Presumptive conditions that were never claimed
3. Secondary conditions caused or aggravated by service-connected disabilities
4. Direct conditions supported by service records and a current disability
5. Previously denied conditions that should be reevaluated

Review the complete guide to increasing a VA disability rating before deciding what action, if any, makes sense.

You can also use the free VA Presumptive Condition Checker to research whether your service and diagnosis may fit a current presumptive category.

For potential secondary conditions, review the complete VA secondary-conditions list.

Keep Your Ratings and Evidence Organized

When a veteran has several service-connected disabilities, it can become difficult to track:

• Individual percentages
• Effective dates
• Pending claims
• Secondary-condition possibilities
• Previous denials
• Supporting medical evidence
• Changes in symptoms

The paid VA Claims Strategy Dashboard provides a structured place to organize your strategy.

If you are at the beginning of the process and still identifying potential conditions, download the free VA Disability Brainstorm Worksheet.

These resources are organizational and educational tools. They do not determine eligibility or guarantee a particular rating.

Final Thoughts

The bilateral factor is easy to misunderstand because it sounds like VA simply adds 10% to a veteran’s rating.

That is not how the calculation works.

VA generally:

• Identifies the qualifying compensable disabilities on both sides
• Combines those disability percentages
• Adds 10% of the combined bilateral value
• Treats the adjusted result as one disability
• Continues the remaining VA-math calculation
• Rounds the final combined evaluation according to the applicable rule

The adjustment can matter, especially when several disabilities are involved. But it may not always change the final rounded rating.

The best first step is to list every individual rating, confirm its effective date, and calculate the result before deciding that anything was missed.

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