How VA Calculates Combined Disability Ratings

This is the single most misunderstood piece of math in the entire VA disability system. If you take away one thing from this article: your ratings do not add together.

The "whole person" concept

Rather than simple addition, the VA treats each rating as reducing your remaining "efficiency," starting from 100% and working down. Think of it like this: your first rating takes its percentage off the top. Your second rating then applies to whatever's left, not to the original 100%. This is why combining two 40% ratings produces something closer to 64%, not 80%, and why it becomes genuinely difficult to reach 100% by stacking moderate ratings.

The formula

For any two ratings A and B (using the larger one as A):

Combined = A + B × (100 − A) / 100

In plain language: take your highest rating first. Then add your next rating's share of whatever percentage is "left over" after the first one.

A worked example

Say you have three ratings: 50%, 30%, and 20%. Order them from highest to lowest first, since order matters.

Start with 50%. That leaves 50% "remaining."
Apply the 30% rating to that remaining 50%: 30% of 50 is 15. Add that to your 50, giving you 65%.
Apply the 20% rating to what's left (35% remaining): 20% of 35 is 7. Add that to your 65, giving you 72%.
Round to the nearest 10%. 72% rounds to 70%.

Your combined rating would be 70%, not the 100% you'd get from simply adding 50 + 30 + 20.

The bilateral factor

If you have ratings affecting paired limbs (both knees, both arms, etc.), the VA applies a "bilateral factor": it combines the two paired ratings first, then adds an extra 10% of that combined figure before folding the result into your overall combined rating. This slightly boosts your total compared to treating the two limbs as unrelated ratings.

Using the official Combined Ratings Table

The VA's Combined Ratings Table (found in 38 CFR § 4.25) does this same calculation in a grid format so you don't have to do the multiplication by hand: find your highest rating along one axis, your next-highest along the other, and the intersection gives you the combined value. Repeat with each additional rating, always folding the running combined total back into the table for the next comparison.

Why this matters beyond curiosity

Understanding this math helps you set realistic expectations before filing for an increase, and it's part of why TDIU (see the separate guide) exists: because VA math makes a 100% combined rating hard to reach even for veterans whose disabilities genuinely prevent them from working. If your combined rating is landing lower than you expected, this formula is usually why, not necessarily an error in your claim.