VA Disability Math: Why 50 + 30 ≠ 80

The VA isn't adding disabilities. It's subtracting efficiency.

Every confused conversation about combined ratings dissolves once you see the model the regulation actually uses. 38 CFR §4.25 doesn't treat you as a pile of percentages to sum. It treats you as a whole person with an efficiency that each disability reduces in turn.

The regulation's own worked example:

"a person having a 60 percent disability is considered 40 percent efficient. Proceeding from this 40 percent efficiency, the effect of a further 30 percent disability is to leave only 70 percent of the efficiency remaining after consideration of the first disability, or 28 percent efficiency altogether. The individual is thus 72 percent disabled."

So 60 and 30 combine to 72, not 90. The second rating applies to what's left, not to the whole. Each additional disability takes a bite out of a smaller and smaller remainder — which is why stacking 10% ratings never gets you anywhere near 100%, and why the tenth one is nearly worthless while the first is not.

The procedure, in order

§4.25(a) is precise about sequence, and the sequence matters:

1. Arrange disabilities in exact order of severity, greatest first.
2. Combine the first two using Table I — read one in the left column, the other in the top row; the intersection is the combined value.
3. Combine that value — exactly as found in the table, unrounded — with the third, and so on for four or more.
4. Round only at the very end, to the nearest number divisible by 10, adjusting final 5s upward.

§4.25(b) makes the rounding rule explicit: the conversion happens only once per rating decision, after all disabilities are combined, as the last procedure. Rounding intermediate values is the single most common way people mis-predict their own rating.

That first row answers the title question: 50 + 30 = 80 is wrong, but 50 + 30 = 70 is right — and it's right for two reasons stacked on each other. The table gives 65, and the rounding rule pushes the 5 up rather than down.

The bilateral factor — the 10% almost nobody claims correctly

§4.26 adds something most calculators get wrong. When a partial disability affects both arms, both legs, or paired skeletal muscles, you combine the right and left side ratings as usual and then add 10 percent of that value — added, explicitly not combined — before proceeding with further combinations.

The regulation's example: disabilities of 60, 20, 10 and 10, where the two 10s are bilateral. The two 10s combine to 19; the bilateral factor makes it 21. Order of severity becomes 60, 21, 20. Then 60 and 21 combine to 68, and 68 and 20 combine to 74 — rounded to 70.

Two details that get missed:

• Apply the bilateral factor first, before other combinations, and then treat the result as a single disability for ordering and all further combining.
• "Arms" and "legs" mean whole extremities. §4.26(a) is clear that the terms aren't meant to distinguish arm from forearm from hand, or thigh from leg from foot — they mean the upper and lower extremities as a whole. A right thigh amputation and left foot pes planus qualify as bilateral.

If you have compensable conditions on both sides of your body, check whether the bilateral factor was applied. It's a rounding-threshold-sized adjustment, and rounding thresholds are where whole ratings tiers are won.

Why the thresholds matter more than the number

Combined ratings are converted to multiples of 10, and the money and eligibility both live at those steps — not in between. Practical consequences:

• A combined 65 and a combined 74 are both worth exactly one thing: the tier they round to. 65 rounds to 70; 74 rounds to 70. One more small condition on the 74 could push you to 80; on the 65 it might not.
• 50% is the CRDP line. A retiree rated 50% or higher receives full retired pay and full VA compensation without the usual dollar-for-dollar offset (10 U.S.C. §1414). Below 50%, the waiver applies. That single threshold is worth more than most rating increases — see our CRDP guide.
• Ratings drive other benefits too, including the VA home loan funding fee waiver — see our funding fee guide.

Also worth knowing: under §4.25(b), disabilities arising from a single disease entity — arthritis, multiple sclerosis, a cerebrovascular accident — are rated separately like any other conditions, then combined. One diagnosis can legitimately produce several ratings.

What this means when you file

• Claim everything documented, even the small things. A 10% condition added to a low combined total moves you meaningfully; the same 10% added to an 80% total barely registers. Claim early in your career-end sequence, when your remainder is still large.
• File in the BDD window if you can — 180 to 90 days before separation. See our BDD timeline guide.
• Don't try to reverse-engineer a target. You claim conditions, not percentages; the rating follows the evidence. What this math is genuinely useful for is understanding why a decision came out where it did — and whether a supplemental claim is likely to change your tier or just your unrounded value.

Sources

• 38 CFR §4.25 (as of 1 July 2026) — the combined ratings table and its efficiency model; (a) ordering by severity, reading Table I, combining unrounded intermediate values, converting to the nearest multiple of 10 with final 5s adjusted upward; (b) single disease entities rated separately, and conversion done only once per rating decision as the last procedure
• 38 CFR §4.26 (as of 1 July 2026) — the bilateral factor: combine both sides as usual, add (not combine) 10 percent of that value, apply before other combinations, treat as one disability thereafter; (a) "arms" and "legs" mean the upper and lower extremities as a whole
• Authority for both: 38 U.S.C. §1155
• 10 U.S.C. §1414 — the 50% CRDP threshold · Current VA disability compensation rates (effective 1 Dec 2025) and 2026 SMC rates, for what each tier pays

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