Most veterans assume two 50 percent ratings make 100. VA math says they make 80: under 38 CFR 4.25 each new rating chips away only at the efficiency you have left, which is why the numbers slow to a crawl near the top. Understanding the arithmetic explains both why the last 10 points are the hardest and why TDIU and SMC exist as alternate routes to the 100 percent rate.
VA math is not regular math
When VA combines disability ratings, it does not add them. Two 50 percent ratings do not make 100. VA uses the Combined Ratings Table at 38 CFR 4.25, which is built on the idea of remaining efficiency. Think of yourself as starting at 100 percent efficient. Each disability takes a slice of whatever efficiency is left, not a slice of the original whole.
Step by step
- Order your ratings from highest to lowest.
- Apply the first (highest) rating to 100 percent efficiency.
- Apply the next rating to the efficiency that remains.
- Keep going until every rating is used.
- Round the final number to the nearest 10 (45 to 49 rounds to 50; 44 and below rounds to 40).
Example: two 50 percent ratings
- Start at 100. A 50 percent rating leaves you 50 percent efficient.
- The second 50 percent applies to the remaining 50, removing 25. You are left at 25 percent efficient.
- Disability is 100 minus 25, which is 75. Rounded to the nearest 10, that is 80 percent, not 100.
Example: 70, 50, and 30
- 70 leaves 30 efficient.
- 50 of the remaining 30 removes 15, leaving 15 efficient.
- 30 of the remaining 15 removes about 4.5, leaving about 10.5 efficient.
- Disability is about 89.5, rounding to 90 percent.
The Combined Ratings Table does this arithmetic for you, but the logic above is what it encodes.
The bilateral factor
If you have disabilities affecting both arms, both legs, or paired skeletal muscles, the bilateral factor (38 CFR 4.26) adds an extra 10 percent of the combined value of those paired disabilities before they are combined with everything else. It rewards the compounding effect of losing function on both sides. One narrow exception was added in 2023; see the bilateral factor explained for the rule and the Federal Register change.
No double counting
The anti-pyramiding rule (38 CFR 4.14) stops VA from rating the same symptom twice under two diagnostic codes. Separate ratings are proper only when they cover distinct disabling effects.
From percentage to dollars
Your combined percentage maps to a monthly dollar amount on the VA compensation rate tables, and the amount goes up if you have a spouse, children, or dependent parents. A higher percentage is worth more both as a base rate and through larger dependent add-ons.
The gap above 90 percent
Going from 90 to 100 percent is the biggest single jump in the system, and the hardest to reach by combination. Two other paths get you to the 100 percent rate without a 100 percent schedular number:
- TDIU, if your conditions prevent substantially gainful employment (38 CFR 4.16). See the TDIU guide.
- Special Monthly Compensation (SMC) under 38 CFR 3.350, which pays above the 100 percent rate for specific losses or for needing aid and attendance. See SMC explained.
Try the numbers yourself with our combined rating calculator.
When you check VA's math, ask
- Are the ratings ordered from highest to lowest and applied to the remaining efficiency, with the final figure rounded to the nearest 10?
- Do disabilities on both arms, both legs, or paired skeletal muscles get the bilateral factor under 38 CFR 4.26 before they combine with everything else?
- Is any rating pair compensating the same symptom twice? The anti-pyramiding rule at 38 CFR 4.14 cuts both ways.
- If the combined number stalls at 80 or 90, do the facts support TDIU (38 CFR 4.16) or SMC (38 CFR 3.350) instead of chasing more percentage points?
- Are dependents added once the combined rating reaches 30 percent, where the monthly rate rises for a spouse, children, or dependent parents?
Related on this site
- Combined ratings, the long-form explainer
- The bilateral factor, explained
- Special Monthly Compensation (SMC), explained
- Combined rating calculator
Common questions
Why do two 50 percent ratings not equal 100 percent?
Because VA does not add ratings; it combines them using the Combined Ratings Table at 38 CFR 4.25, built on remaining efficiency. A 50 percent rating leaves you 50 percent efficient; the second 50 percent applies to the remaining 50, removing 25 more. That leaves 25 percent efficiency, so disability is 75, which rounds to 80 percent, not 100.
How do I calculate my combined VA rating?
Order your ratings from highest to lowest, apply the highest to 100 percent efficiency, then apply each next rating to the efficiency that remains, and round the final number to the nearest 10 (45 to 49 rounds up to 50; 44 and below rounds down to 40). Example: 70, 50, and 30 leaves about 10.5 percent efficiency, which is about 89.5 disability, rounding to 90 percent.
What is the bilateral factor?
When disabilities affect both arms, both legs, or paired skeletal muscles, 38 CFR 4.26 adds an extra 10 percent of the combined value of those paired disabilities before they are combined with everything else. It accounts for the compounding effect of losing function on both sides.
How do I reach the 100 percent rate if the math stalls at 90?
The jump from 90 to 100 is the hardest to reach by combination, but two paths pay the 100 percent rate without a 100 percent schedular number: TDIU under 38 CFR 4.16, when your conditions prevent substantially gainful employment, and Special Monthly Compensation under 38 CFR 3.350, which pays above the 100 percent rate for specific losses or for needing aid and attendance.
What is pyramiding?
The anti-pyramiding rule at 38 CFR 4.14 stops VA from rating the same symptom twice under two diagnostic codes. Separate ratings are proper only when they cover distinct disabling effects, which is why, for example, a spine rating and a separate radiculopathy rating can coexist but two mental health ratings cannot.