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The bilateral factor is one of the most misunderstood elements of VA disability rating math. Most veterans know that the VA uses a "combined ratings" formula rather than simple addition when calculating an overall disability rating. What many do not know is that there is a special provision in 38 CFR 4.26 that provides an additional benefit when a veteran has disabilities affecting both sides of the body. This provision, known as the bilateral factor, can increase your combined rating in situations where you have qualifying paired disabilities.
To understand the bilateral factor, you first need to understand how the VA combines ratings. The VA does not add ratings together. Instead, it uses a formula that accounts for the remaining "efficiency" of the body. If you have a 50% disability, the VA considers you to have 50% remaining efficiency. A second 30% disability is applied to that remaining 50%, reducing it by 30% of 50 (which is 15), bringing your combined value to 65%. This is why two 50% ratings do not equal 100%. The bilateral factor modifies this calculation when paired disabilities are involved.
The bilateral factor applies to disabilities that affect paired extremities or paired skeletal muscles. Common examples include conditions in both knees, both hips, both shoulders, both ankles, both wrists, both elbows, both feet (such as bilateral plantar fasciitis or bilateral flat feet), and bilateral hearing loss. The key requirement is that the conditions must affect corresponding body parts on both the left and right sides. A left knee condition and a right knee condition would qualify. A left knee condition and a right shoulder condition would not, because they are not a matched pair.
Here is how the bilateral factor works mathematically. First, the VA combines the ratings for the qualifying bilateral conditions using the standard combined ratings formula. Then, the VA adds 10% of that combined bilateral value to the result. This adjusted bilateral value is then combined with any remaining non-bilateral disabilities using the standard formula. The effect is that the bilateral disabilities receive a small boost before being merged into the overall calculation.
Let us walk through a concrete example. Suppose a veteran has a 20% rating for left knee degenerative arthritis and a 10% rating for right knee degenerative arthritis. Using the combined ratings table, 20% combined with 10% gives a bilateral combined value of 28%. The bilateral factor adds 10% of 28, which is 2.8, rounded to 3. So the adjusted bilateral value becomes 31%. This 31% is then combined with any other service-connected disabilities using the standard formula. Without the bilateral factor, the bilateral combined value would have entered the calculation as 28% rather than 31%.
A more complex example illustrates the impact more clearly. Consider a veteran with 30% for left knee instability, 20% for right knee limitation of motion, 10% for left knee arthritis, and 40% for PTSD. The bilateral knee ratings (30%, 20%, and 10%) are first combined together: 30 combined with 20 equals 44, and 44 combined with 10 equals 50. The bilateral factor adds 10% of 50, which is 5, making the adjusted bilateral value 55%. Then 55% is combined with the 40% PTSD rating using the standard formula: 55 combined with 40 equals 73, which rounds to 70% under the VA rounding rules. Without the bilateral factor, the knee ratings alone would have entered as 50% rather than 55%, potentially resulting in a lower final combined rating.
There are important limitations on when the bilateral factor applies. It does not apply to conditions affecting unpaired organs or body parts. For example, if you have a back condition and a neck condition, the bilateral factor does not apply because the spine is a single structure, not a paired extremity. Similarly, conditions affecting the heart, lungs (as a single organ system), or digestive system do not qualify for the bilateral factor. The factor is specifically designed for the increased functional impairment that comes from having both sides of a paired body part affected.
Bilateral hearing loss is a common condition where the bilateral factor applies but is often overlooked. If you have service-connected hearing loss in both ears, the VA should apply the bilateral factor to your hearing loss ratings. Hearing loss ratings are determined through a specific formula based on audiometric test results and speech recognition scores, and they often result in relatively low individual ratings. The bilateral factor provides a small but meaningful boost in these cases.
Veterans should verify that the bilateral factor was correctly applied in their rating decision. The VA rating decision letter and the accompanying rating codesheet should show the intermediate calculations, including the bilateral factor adjustment. If you have qualifying bilateral conditions and the bilateral factor was not applied, this could be an error that, if corrected, might increase your overall combined rating. Reviewing your rating math carefully, or asking a VSO or representative to review it, is a worthwhile step after receiving any rating decision.
Disclaimer: This article is for educational and informational purposes only. It does not constitute legal, medical, or VA claims advice. VA regulations, fee structures, and enforcement actions are subject to change. Always verify current requirements at VA.gov or consult with an accredited VSO, attorney, or claims agent before making decisions about your benefits.
Written by Claim Recon Editorial