"VA math" is the single most confusing part of understanding disability compensation, and it trips up nearly every veteran the first time they see it. If you have a 50% rating and a 30% rating, your combined rating is not 80%. Here's why, and how to actually calculate it.
The Core Idea: Whole Person Theory
The VA doesn't add ratings — it treats you as a whole, undamaged person at 100% efficiency, and each disability rating chips away at whatever capacity you have left, not the original 100%.
Worked example: You have a 50% rating and a 30% rating. Start at 100% efficiency. The 50% rating removes half, leaving you at 50% efficiency. The 30% rating is then applied to that remaining 50%, not the original 100% — 30% of 50 is 15. So your combined value is 50 + 15 = 65%, which the VA then rounds to the nearest 10%, giving you a final combined rating of 70% — not 80%.
Using the Combined Ratings Table
In practice, the VA doesn't do this arithmetic freehand — they use a published Combined Ratings Table where you cross-reference your two highest ratings to get the combined value directly, then repeat with each additional rating (always combining your current running total with the next disability, highest ratings first).
| Rating 1 | Rating 2 | Combined (before rounding) | Final Rating |
|---|---|---|---|
| 50% | 30% | 65% | 70% |
| 40% | 20% | 52% | 50% |
| 60% | 40% | 76% | 80% |
| 70% | 50% | 85% | 90% |
Notice the pattern: combining ratings always produces a number lower than simple addition would suggest, because each additional rating is applied to a progressively smaller remaining base.
The Bilateral Factor
There's one wrinkle that can work in your favor: the bilateral factor. If you have compensable ratings affecting both arms, both legs, or paired skeletal muscles/joints, the VA first combines those two paired ratings, then adds an extra 10% on top of that combined figure before folding it in with your other ratings. This exists because losing function in both of a paired body part is considered more limiting than the same two ratings on unrelated body parts — for example, a knee and a shoulder.
Why Order Matters
When combining three or more ratings, the VA always starts with your highest rating and works down. Combining in a different order can produce a different intermediate rounding result, so this isn't just a formality — it's part of why manually calculating combined ratings with several conditions gets error-prone quickly.
Just Use a Calculator
Most veterans don't do this table lookup by hand past two ratings — they use an online VA combined ratings calculator, which applies the Combined Ratings Table and bilateral factor automatically. The math above is worth understanding so you know why the number came out the way it did, especially when reviewing a decision letter or deciding whether an appeal is worth pursuing.