Most veterans assume 50 plus 50 equals 100. In VA math it equals 80, because VA does not add ratings, it combines them against the efficiency you have left.
Why VA combines instead of adds
VA does not add your disability percentages. It combines them using the table at 38 CFR 4.25, which is built on the idea of whole-person efficiency. Start at 100 percent efficient. Each disability removes a share of the efficiency that is still left, never a share of the original whole. That is why two 50 percent ratings combine to about 75 (then round to 80), not 100.
The method, step by step
- Order your ratings highest to lowest.
- Apply the first rating to 100 percent efficiency.
- Apply the next rating to the efficiency that remains.
- Continue until every rating is used.
- Round the final value to the nearest 10 (45 to 49 rounds up to 50; 44 and below rounds down to 40).
A worked example
70, then 50, then 20:
- 70 leaves 30 efficient.
- 50 of the remaining 30 removes 15, leaving 15.
- 20 of the remaining 15 removes 3, leaving 12.
- Disability is 100 minus 12, which is 88, rounding to 90 percent.
The 10 percent rule and why a new condition adds less than you expect
Because each rating bites only into what is left, a new condition added near the top of a high combined rating barely moves the needle. If you are already combined to 90 and VA grants a new 10 percent condition, that 10 applies to the 10 percent of efficiency you have left, removing just 1 point. After rounding, your combined rating often does not change at all. This surprises people who expect 90 plus 10 to equal 100.
The bilateral factor
Disabilities affecting both arms, both legs, or paired muscles get an extra 10 percent of their combined value added before they are folded into the rest (38 CFR 4.26). It recognizes the compounding effect of losing function on both sides. See the bilateral factor explained, including the narrow 2023 exception.
No double counting
The anti-pyramiding rule (38 CFR 4.14) prevents VA from rating the same symptom twice under two codes. Separate ratings are proper only for distinct disabling effects.
The nuances most veterans miss
- A small rating at the top can add zero. Added to a high combined number, a 10 percent condition may round away to no change, even though it is a real, separately listed disability.
- Order does not change the math, only the bookkeeping. The table is symmetric, but always working highest first keeps it clean.
- Reductions use the same table. If a rating drops, the combined value is recalculated the same way.
- The gap to 100 is the hardest. When combination stalls at 90, the two other doors to the 100 percent rate are TDIU (38 CFR 4.16) and Special Monthly Compensation (38 CFR 3.350).
- Try the numbers. Our combined rating calculator does the table for you.
When you read your combined rating, ask
- Does each listed rating appear in the calculation, ordered highest to lowest?
- Was the bilateral factor applied to paired limbs before the rest of the math (38 CFR 4.26)?
- Did the final value round correctly, 45 to 49 up, 44 and below down?
- If you are stalled at 90, have you looked at TDIU and Special Monthly Compensation as the other doors to the 100 percent rate?
Related on this site
- VA math: how combined ratings really work
- The bilateral factor, explained
- Special Monthly Compensation (SMC), explained
- Combined rating calculator
Common questions
How does VA combine multiple disability ratings?
With the whole-person efficiency table at 38 CFR 4.25, not addition. Order ratings highest to lowest, apply the first to 100 percent efficiency, then apply each next rating only to the efficiency that remains, and round the final number to the nearest 10. Example: 70, then 50, then 20 leaves 12 percent efficiency, which is 88 disability, rounding to 90 percent.
Why did my new 10 percent rating not change my combined total?
Because each rating bites only into the efficiency that is left. If you are already combined to 90, a new 10 percent condition applies to the 10 percent of efficiency remaining, removing just one point, and after rounding the combined rating often does not move at all. The new condition is still real and separately listed; it just adds less than expected near the top.
What is the bilateral factor?
When disabilities affect both arms, both legs, or paired muscles, 38 CFR 4.26 adds an extra 10 percent of their combined value before they are folded into the rest of the math. It recognizes the compounding effect of losing function on both sides.
How do I get from 90 to 100 percent?
The gap to 100 is the hardest to close by combination alone. The two other doors to the 100 percent rate are TDIU under 38 CFR 4.16, when service connected disabilities prevent substantially gainful employment, and Special Monthly Compensation under 38 CFR 3.350 for specific losses or the need for aid and attendance.