VA Math Is Not Regular Math
If you have two VA disability ratings of 50% and 30%, you'd expect your combined rating to be 80%. Makes sense, right? 50 + 30 = 80.
But the VA doesn't add ratings together. They use a formula that gives you a lower number every time. It's called "combined ratings math" and it confuses almost everyone who encounters it for the first time.
Once you understand how it works, you can plan better and set realistic expectations for your claim.
How the Formula Actually Works
The VA looks at it this way: you start with a 100% healthy body. Each disability rating takes a percentage away from what's left, not from the original 100%.
Think of it like this. You have 100 health points. Each condition takes a percentage of whatever health points you have remaining.
Let's walk through an example with three conditions.
Step 1: First Condition at 50%
You start at 100% healthy. Your first condition is rated at 50%.
50% of 100 = 50 points of disability.
You now have 50% remaining healthy body. Your combined rating so far: 50%.
Step 2: Second Condition at 30%
Now you add a second condition rated at 30%. But the VA doesn't take 30% of 100. They take 30% of your remaining 50%.
30% of 50 = 15 points of disability.
Total disability: 50 + 15 = 65%. You have 35% healthy body remaining.
See what happened? 50% + 30% gave you 65%, not 80%.
Step 3: Third Condition at 20%
Now add a third condition at 20%. The VA takes 20% of your remaining 35%.
20% of 35 = 7 points of disability.
Total disability: 65 + 7 = 72%.
But the VA rounds to the nearest 10. So 72% rounds down to 70%.
Your final combined rating: 70%. Even though your individual ratings add up to 100% (50 + 30 + 20), the VA math gives you 70%.
Why It Gets Harder to Reach 100%
Every condition you add takes a percentage of a shrinking number. The more conditions you have, the less each new one moves the needle.
Let's say you're at 90% combined and you get a new 10% rating. The VA takes 10% of your remaining 10%. That's 1 point. You go from 90% to 91%, which rounds to 90%.
That new condition literally changed nothing on paper. This is why getting from 90% to 100% through combined ratings alone is extremely difficult. You would need a single condition rated very high, or several conditions that push the combined math past 95% (which rounds up to 100%).
The Bilateral Factor
There's one exception that works slightly in your favor. If you have disabilities affecting both arms, both legs, or paired organs (like both knees or both shoulders), the VA adds a "bilateral factor" of 10% to the combined value of those paired conditions before plugging them into the formula.
For example, if you have 20% for your left knee and 10% for your right knee, the VA combines those (28% by VA math), then adds 10% of 28% (2.8%) for the bilateral factor. It's a small bonus, but it helps.
What Is TDIU?
There's another path to 100% pay without needing 100% combined: TDIU. It stands for Total Disability based on Individual Unemployability.
TDIU is for veterans who can't hold a substantial gainful employment because of their service-connected conditions. If your disabilities prevent you from working a steady job, TDIU pays you at the 100% rate even if your actual combined rating is lower.
To qualify for TDIU, you need one of these:
- One condition rated at 60% or higher, or
- A combined rating of 70% or higher, with at least one condition at 40% or higher
You also need to show that your service-connected conditions are what prevent you from maintaining substantially gainful employment. The VA will look at your work history, education, and the nature of your disabilities.
TDIU pays the same monthly amount as a 100% schedular rating. For a single veteran in 2026, that's $3,737.85 per month. With dependents, it goes higher.
If you're rated at 70% or 80% but can't work because of your conditions, TDIU might be the right move. Talk to a Veterans Service Organization (VSO) like the DAV, VFW, or American Legion. They help with claims for free.
How to Use This Information
Knowing how VA math works helps you in two ways.
First, you can set realistic expectations. When you file for an increase or a new condition, you'll know roughly where your combined rating will land.
Second, you can prioritize. If you have multiple conditions to claim, file the highest-rated ones first. The order doesn't technically matter in the final calculation (the VA sorts by highest to lowest automatically), but understanding the math helps you understand your rating decision letter when it comes back.
Calculate Your Combined Rating
Want to run the numbers yourself? Use our VA Disability Calculator to plug in your individual ratings and see your combined result instantly. It uses the exact same formula the VA uses, including rounding rules.
Know your numbers. Know your benefits. That's how you make sure you're getting what you earned.