Q. How does VA calculate compensation rates?
A. VA makes a determination about the severity of your disability based on the evidence you submit, your military records, and compensation and pension medical examination reports. VA rates disability from 0 percent to 100 percent in 10 percent increments.
If VA finds that a veteran has multiple disabilities, the VA will use the Combined Ratings Table to calculate a combined disability rating. Disability ratings are not additive, meaning that if a veteran has one disability rated 60 percent and a second disability rated 20 percent, the combined rating is not 80 percent.
Visit the Combined Ratings Table to understand the steps VA takes to combine ratings for more than one disability — the degree of one disability will be read in the left column and the degree of the other in the top row. Combined Ratings Table: www.benefits.va.gov/compensation/rates-index.asp 
For example, if a veteran has a 50 percent disability and a 30 percent disability, the combined value is 65 percent. The 65 percent must be converted to 70 percent because the combined value is rounded to the nearest 10 percent to represent the final degree of disability. Similarly, if a veteran has a 40 percent disability rating and another disability rating of 20 percent, the combined value is 52 percent. The 52 percent must be converted to the nearest degree divisible by 10, which is 50 percent.
When combining three disability ratings, such as 60, 40 and 20 percent, find the combined value for the first two, which would be 76 percent. The intersection of 76 percent and the third disability rating of 20 percent is 81. And the final rating is rounded to 80 percent.