How does the VA calculate combined disability to reach 100%?
Executive summary
The VA does not add individual ratings together; it combines them using a “VA math” method that treats each rating as a percentage of the remaining non‑disabled portion and then uses a combined ratings table, so the final combined rating never exceeds 100% (for example, two 10% ratings combine to 19%) [1] [2]. Private calculators mirror the VA table and explain the stepwise approach and rounding rules veterans encounter when multiple conditions or bilateral factors apply [3] [4].
1. How the VA actually combines percentages — the stepwise “VA math”
The VA orders disabilities from largest to smallest, then applies each subsequent rating to the remaining healthy portion rather than adding percentages directly. In effect, a 10% rating means the veteran is 90% “efficient” (healthy), so the next disability’s percentage reduces that remaining efficiency; the VA provides combined ratings tables and an online calculator that implement this method [1] [2]. Multiple independent explainer sites describe the same logic, calling it “VA math” and noting VA staff refer to an internal tool sometimes called the Combinator [5] [3].
2. Why the combined rating can’t exceed 100% — and when extra pay can still apply
Because the process applies each new rating to what’s left of the veteran’s functional capacity, the combined number is capped at 100% disability on the standard scale; however, veterans with severe losses may receive additional Special Monthly Compensation (SMC) beyond a 100% combined rating under other VA rules — private guides flag that distinction when explaining that combined ratings top out but extra compensation can still occur [6] [7].
3. What the Combined Ratings Table and rounding rules do
The VA supplies combined ratings tables so pairwise combinations map to a single combined figure; once you combine two ratings you repeat the process with the next rating until all are included [4] [2]. The tables produce intermediate numbers that VA then converts to the nearest official rating increment (ratings are expressed in 10% steps, with some standard rounding conventions) — for example, a calculated 66% can be rounded to an official 70% combined rating in VA examples [4] [2].
4. Bilateral factor and special adjustments — when the formula changes
Several private explainers and VA guidance note that the bilateral factor (a separate rule that increases combined value when both limbs or paired organs are affected) and other statutory exceptions can alter the final compensation calculation beyond straightforward table math; calculators include these elements because they can materially change pay even when combined ratings themselves are governed by the table method [6] [7].
5. Practical example used by calculators to show the math
Common worked examples show the mechanics: combine the two largest ratings using the table to get an interim value, then intersect that result with the third rating to get the next value, repeating until all ratings are applied — a set of three ratings that calculates to an interim 66% will typically be shown as 70% after the VA’s conversion rules [4] [8]. Consumer-facing tools and law‑firm calculators replicate the VA process so veterans can preview likely outcomes [5] [9].
6. Where confusion and complaints come from
Veterans and advocates report frustration because the VA’s approach feels counterintuitive: people expect additive math but VA applies percentages sequentially, which often yields lower combined totals than simple sums; law firms and outreach groups say veterans frequently ask “How in the world did VA get that combined rating?” and build calculators to explain the result [5] [3]. The VA itself warns that combined ratings are not additive and points users to online tables and calculators to reduce confusion [1] [2].
7. Limits of available reporting and next steps for veterans
Available sources explain the formula, tables, bilateral factor, and that SMC can add pay beyond 100%, but they do not provide VA’s internal code or the exact “Combinator” implementation details beyond what’s visible in the public tables and calculator (not found in current reporting). Veterans who want a definitive number should use the VA’s own combined ratings calculator or the official Combined Ratings Table on VA.gov and confirm whether bilateral factor or SMC criteria apply to their case [1] [10].
Sources cited: VA public guidance and combined ratings table [1] [2]; private law‑firm and calculator explainers that reproduce VA math and offer worked examples [5] [3] [4] [9]; consumer sites and benefits pages describing caps, SMC and bilateral factor [7] [6] [8].