Here is the single most useful fact about VA disability math: ratings do not add. A veteran with a 50 percent condition and a 30 percent condition is not 80 percent disabled. The VA combines ratings using a whole-person method set out in 38 CFR 4.25, and once you understand that method, the numbers stop feeling random. This guide explains the mechanism, walks a worked example straight from the regulation, and shows where the bilateral factor changes the math.
Why ratings combine instead of add
The VA does not treat you as a stack of percentages that can pile past 100. It treats you as a whole person whose efficiency is reduced by each disability in turn. The regulation puts it in plain arithmetic. In the words of 38 CFR 4.25, "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."
Read that slowly, because it is the whole idea. Your first disability takes its share of the whole person. The next disability takes its share of what is left, not of the original whole. That is why each additional condition adds less to your combined rating than its face value suggests. A 28 percent efficiency in that example means roughly a 72 percent combined disability, which is simple subtraction from 100 once the regulation has done the efficiency step.
The order rule and the rounding rule
Two smaller rules control the final number.
First, order. The regulation directs that "the disabilities will first be arranged in the exact order of their severity, beginning with the greatest disability." You always start the combination with your single most severe rating and work down. Because each condition only reduces the remaining efficiency, the starting point matters.
Second, rounding. After everything is combined, the regulation states, "This combined value will then be converted to the nearest number divisible by 10, and combined values ending in 5 will be adjusted upward." That single sentence answers the question you probably came here with.
| Step | What happens | Result |
|---|---|---|
| Combine 50 and 30 | Whole-person combination, not addition | Combined value 65 |
| Apply the rounding rule | Convert to nearest number divisible by 10, values ending in 5 go up | 70 percent |
The regulation itself uses this exact example, noting that a combined value of 65 percent "must be converted to 70 percent." So 50 and 30 is 70, not 80, and the reason is a rounding rule you can now cite.
One more piece of discipline the regulation builds in: rounding happens once and last. Per 38 CFR 4.25, "The conversion to the nearest degree divisible by 10 will be done only once per rating decision, will follow the combining of all disabilities, and will be the last procedure in determining the combined degree of disability." If you have three or four conditions, you combine all of them first and round a single time at the end. Rounding along the way would give the wrong answer.
The bilateral factor: extra math for paired limbs
There is a special rule when disabilities affect paired parts of the body. Under 38 CFR 4.26, "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)."
That "added, not combined" language is the whole point. Normally the VA combines, which yields less than a straight sum. The bilateral factor is the rare place where a piece is added on top. When four extremities are involved, the regulation directs the VA 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."
For this rule, "arms" and "legs" mean the paired upper and lower extremities as wholes, regardless of where along the limb the impairment sits, and the factor applies only where there is compensable partial disability in each of two paired extremities or paired skeletal muscles.
Hypothetical example. Suppose a veteran has a service-connected condition in the right leg and a separate service-connected condition in the left leg. Because both legs are involved, the VA combines the two leg ratings in the usual way, then adds 10 percent of that combined value on top before folding the result in with any other ratings and rounding once at the end. The exact figure depends on the specific ratings, which is why you should route the calculation to the combined rating calculator rather than guessing.
Why extra conditions add less near the top
The efficiency method has a practical consequence worth internalizing. Because each new disability only reduces the efficiency that remains, a condition added when your combined rating is already high moves the total far less than its face value suggests. A condition that would mean a lot on its own can nudge a high combined rating only slightly, simply because there is less remaining efficiency for it to reduce. That is not the VA shortchanging you. It is the same whole-person arithmetic applied consistently from your most severe condition down to your least. It also means the combined total can approach but never simply pile past the maximum, because you cannot be rated as more than a whole person. Keeping this in mind grounds your expectations when you add a new claim to an existing rating, and it is exactly why running the real figures beats doing the sum in your head.
Put the numbers in the calculator
The rules above are the concepts. The arithmetic, especially with three or more conditions, an order-of-severity sort, and a bilateral factor, is where hand estimates go wrong. Enter your individual ratings into the combined rating calculator and let it apply the table, the order rule, the bilateral factor, and the single final rounding for you. Then read what the resulting combined rating means for your monthly amount in VA Disability Compensation Explained.
What this does not mean
A combined rating is not the sum of your conditions, and it is not a measure of how sick you feel. It is a whole-person efficiency figure produced by a fixed formula. Two veterans with the same list of conditions but different individual ratings can land on different combined numbers, and adding your percentages in your head will usually overstate the result.
How to sanity-check your own decision
When you get a rating decision, you can verify the VA applied the method correctly. Confirm your conditions were arranged from most to least severe, that the bilateral factor was applied if paired limbs are involved, and that rounding happened only once at the end. Learning to read the decision line by line is its own skill, covered in How to Read Your VA Rating Decision. If something looks off, browse the VA ratings reference and the conditions library, and learn any unfamiliar term in the glossary. We educate and help you organize your evidence. We never prepare or file your claim.