Every veteran who files for multiple service-connected conditions eventually hits the same wall of confusion: if I have a 50% rating and a 30% rating, why doesn’t that equal 80%? The answer is VA math — and once you understand it, you’ll understand why getting to 100% requires more than you think.
Step-by-Step: How to Calculate Your Combined Rating
Step 1: List your disabilities from highest to lowest rating. Step 2: Apply the highest rating first — that takes 50% of your “whole person,” leaving 50% remaining efficiency. Step 3: Apply the next rating as a percentage of what remains. A 30% disability applied to 50% remaining = 15%. Combined so far: 65. Step 4: Round to the nearest 10% — 65 rounds to 70%.
Add a third disability at 10%: apply 10% to the 35% remaining (after 50% and 30%) = 3.5%. New total: 68.5, rounded to 70%. The third disability added almost nothing to the combined rating.
Why Getting from 90% to 100% Is Hard
By the time you’re at 90%, you have almost no remaining efficiency for additional ratings to work against. A 10% disability applied to the remaining 10% = 1%. Your combined goes from 90 to 91, which rounds to 90. To get from 90% to 100% through additional conditions alone is effectively impossible using the standard combined rating method — which is why TDIU exists.
The Bilateral Factor
If you have service-connected disabilities affecting both sides of the body (both knees, both shoulders, both arms), the VA applies a 10% bilateral factor to the combined value of those paired disabilities before combining with your other conditions. This adds real value — don’t overlook it when building your claim.
TDIU as the Path to 100% Pay
Total Disability Individual Unemployability (TDIU) pays at the 100% rate if your service-connected disabilities prevent you from maintaining substantially gainful employment. You qualify for TDIU with a single disability at 60%+, or a combined rating of 70%+ with at least one disability at 40%+. TDIU is how many veterans get 100% compensation without reaching a 100% combined rating.
Does the order of disabilities in VA math matter?
In theory no — the final combined rating is the same regardless of order. In practice, always list your highest-rated condition first when calculating to keep the math intuitive.
What if I think my combined rating was calculated wrong?
Request your rating decision and walk through the math yourself using the VA’s combined ratings table. If you find an error, file a Higher-Level Review — a clear calculation error is exactly what that lane is designed for.
Does a 0% service-connected rating count toward TDIU eligibility?
No. Only compensable ratings (10% and above) count toward the combined rating threshold for TDIU eligibility. However, a 0% rating still establishes service connection and can be claimed for an increase if the condition worsens.