The Bilateral Factor: 38 CFR 4.26, Worked Step by Step

It is an extra step in the combining math that runs before the rest of it. 38 CFR 4.26 opens with the whole rule in one sentence: 'Except as provided in paragraph (d) of this section, 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 usual, and 10 percent of this value will be added (i.e., not combined) before proceeding with further combinations, or converting to degree of disability.'

Two words in that sentence carry most of the weight. Added, and not combined. Ten percent of the paired value is ordinary addition, and it is the only place in this procedure where addition happens at all.

The next sentence sets the position in the order: 'The bilateral factor will be applied to such bilateral disabilities before other combinations are carried out and the rating for such disabilities including the bilateral factor in this section will be treated as one disability for the purpose of arranging in order of severity and for all further combinations.'

So the group goes in first, comes out as a single number, and is then treated as a single condition for ordering and for everything downstream. 38 CFR 4.25, which holds the combined ratings table, never mentions the word bilateral and never cross-references 4.26. The table receives a number that this rule has already produced.

More than most people expect. The regulation defines its own terms at paragraph (a), and the definition is deliberately broad.

'The use of the terms "arms" and "legs" is not intended to distinguish between the arm, forearm and hand, or the thigh, leg, and foot, but relates to the upper extremities and lower extremities as a whole. Thus with a compensable disability of the right thigh, for example, amputation, and one of the left foot, for example, pes planus, the bilateral factor applies, and similarly whenever there are compensable disabilities affecting use of paired extremities regardless of location or specified type of impairment.'

A right thigh and a left foot are a pair. The regulation says so with its own example. The conditions do not have to match, they do not have to sit at the same joint, and they do not have to be the same type of impairment. What matters is that both lower extremities are affected, or both upper extremities.

Paired skeletal muscles are covered by the same rule, on the same terms.

What is not a pair: one arm and one leg. Those are not paired extremities, and no reading of paragraph (a) makes them so.

No. Paragraph (c) is one sentence and it is unambiguous: 'The bilateral factor is not applicable unless there is partial disability of compensable degree in each of 2 paired extremities, or paired skeletal muscles.'

Compensable degree means an evaluation above 0 percent. A 10 percent knee on the right and a 0 percent knee on the left do not satisfy this. Both sides have to carry a compensable evaluation on their own before there is a pair to apply anything to.

This is the most common reason a reader who expected the factor does not find it on their letter, and it is worth checking first, before checking the math. The evaluations are listed condition by condition on the decision letter. If one side of a supposed pair sits at 0 percent, paragraph (c) has already answered the question.

The regulation works its own example, and reproducing it line by line shows every place a fraction appears.

'For example, with disabilities evaluated at 60 percent, 20 percent, 10 percent and 10 percent (with the two 10 percent evaluations being bilateral disabilities), the order of severity would be 60, 21 and 20. The 60 and 21 combine to 68 percent and the 68 and 20 combine to 74 percent, converted to 70 percent as the final degree of disability.'

Step one, the pair. The two 10 percent evaluations combine to 19. That value is not in the body of Table I, and 38 CFR 4.25 carries a note on the table saying so directly: '[10 combined with 10 is 19]'.

Step two, the addition. Ten percent of 19 is 1.9, and 19 plus 1.9 is 20.9. The regulation then carries the group as 21.

That is worth being careful about. Neither 4.25 nor 4.26 states a rule for rounding the added ten percent. What the regulation does is demonstrate the answer in its own math: 20.9 goes forward as 21. That is what the text shows, not what it says.

Step three, ordering. The group of 21 is now one disability. Order of severity across the file is 60, then 21, then 20, exactly as the regulation prints it.

Step four, combine down the line. 60 with 21 gives 68.4, which Table I carries as 68. 68 with 20 gives 74.4, carried as 74.

Step five, convert, once. 74 converts to 70. Every intermediate value stayed a whole number and none of them was rounded to a ten, because 38 CFR 4.25(b) puts that conversion last and allows it only once per rating decision.

It can, and the cleanest way to see it is to hold the evaluations fixed and move which limb they sit on.

Two evaluations, 30 percent and 20 percent, both in the lower extremities. If they are in opposite legs, they combine to 44, ten percent of 44 is 4.4, and 48.4 goes forward as 48. Convert once: 48 becomes 50.

Now put the same two evaluations in the same leg. There is no pair, so paragraph (c) rules the factor out. They still combine to 44. Convert: 44 becomes 40.

Same two percentages, ten points apart in the final degree of disability, and the entire difference comes from 4.26. Nothing about the medical evidence changed in that comparison, and neither did the combined ratings table. Only the side.

All four go into one group with one ten percent added. Splitting them into an arms group and a legs group, each carrying its own ten percent, is the error paragraph (b) was written against. Paragraph (b) says exactly this: 'The correct procedure when applying the bilateral factor to disabilities affecting both upper extremities and both lower extremities is to combine the ratings of the disabilities affecting the 4 extremities in the order of their individual severity and apply the bilateral factor by adding, not combining, 10 percent of the combined value thus attained.'

Work a case. Evaluations of 30 percent in one leg, 20 percent in the other leg, 20 percent in one arm and 10 percent in the other arm.

Done the way paragraph (b) directs, in order of individual severity across all four: 30 with 20 gives 44. 44 with 20 gives 55.2, carried as 55. 55 with 10 gives 59.5, carried as 60. Ten percent of 60 is 6, and 60 plus 6 is 66. Convert once: 70.

Done as two separate groups, which is the mistake paragraph (b) exists to prevent: the legs combine to 44, plus 4.4, carried as 48. The arms combine to 28, plus 2.8, carried as 31. Then 48 with 31 gives 64.12, carried as 64. Convert: 60.

Seventy against sixty, on the same four evaluations. Two ten percent additions produced a smaller result than one, because the second addition was applied to a much smaller base and the two groups then had to be combined against each other rather than added.

There is a case where applying the factor produces a lower combined evaluation than leaving it out. Since April 2023 the regulation has an answer for it.

38 CFR 4.26(d): 'In cases where the combined evaluation is lower than what could be achieved by not including one or more bilateral disabilities in the bilateral factor calculation, those bilateral disabilities will be removed from the bilateral factor calculation and combined separately, to achieve the combined evaluation most favorable to the veteran.'

That paragraph was added at 88 FR 22917 on April 14, 2023. The section's citation line now reads [29 FR 6718, May 22, 1964, as amended at 88 FR 22917, Apr. 14, 2023], and the opening sentence was amended at the same time to begin 'Except as provided in paragraph (d) of this section'. The rule is younger than most of the calculators that claim to implement 4.26.

Here is a case where it decides the answer. Evaluations of 90 percent, 30 percent, and 10 percent in each arm.

Applying the factor: the two 10 percent evaluations combine to 19, plus 1.9, carried as 21. The 90 and the 30 combine to 93. Then 93 with 21 gives 94.47, which Table I carries as 94. Convert once: 90.

Leaving the two 10 percent evaluations out of the factor and combining them separately: 90 with 30 gives 93. 93 with 10 gives 93.7, carried as 94. 94 with 10 gives 94.6, carried as 95. A combined value of 95 ends in 5, so under 38 CFR 4.25(a) it is adjusted upward. Convert once: 100.

Ninety against a hundred, on the same four evaluations, with the only difference being whether the pair went through the bilateral step. Paragraph (d) directs the outcome most favorable to the veteran, which is the second path.

The reversal comes out of the grouping rather than out of the addition. Bundling the two 10 percent evaluations into a single 21 spends them in one combination against a value of 93, where a 21 is worth about one and a half points. Kept separate, each 10 is combined against the running value in turn and the second one lands the pair just over a rounding boundary. This behavior only shows up near the top of the table, which is why it went unaddressed in the regulation for fifty-nine years.

A calculator built before April 14, 2023 has no reason to check for this, and will still return the 90.

Whether the bilateral factor applies in any particular case. That turns on which conditions were service connected, which extremity each one sits in, and whether each side carries a compensable evaluation. Those facts are on the decision letter. This regulation holds none of them.

It also says nothing about what any evaluation should be. The individual percentages come from the rating criteria in 38 CFR part 4 applied to what the medical record documents. The bilateral factor takes those percentages as given and rearranges the math.

If the math on a letter does not reconcile, a VA-accredited VSO representative will read it with a veteran and does not charge for it. Accredited attorneys and agents can also be appointed and may charge.