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VA Math Explained: How Combined Ratings Work

By VA Disability Hub Editorial Team Last updated: Editorial policy

What Is VA Math?

"VA math" refers to the method the VA uses to combine multiple disability ratings into a single combined rating. Instead of simply adding your ratings together, the VA uses the "whole person" theory defined in 38 CFR § 4.25.

The key concept: each disability rating is applied to your remaining ability, not your total ability. A veteran starts at 100% able-bodied, and each disability reduces a percentage of what remains.

Step-by-Step Example

VA Math infographic showing why 50% + 30% does not equal 80%. Three examples with waterfall bar charts: Two conditions (50% + 30%) = 65%, rounds to 70% (not 80%). Three conditions (50% + 30% + 10%) = 68.5%, rounds to 70% (not 90%). Four conditions (70% + 50% + 20% + 10%) = 89.2%, rounds to 90% (not 150%). Each new rating is applied to remaining ability, not to 100%, which is why combined ratings are always lower than simple addition.
How VA math calculates combined disability ratings — each rating applies to remaining ability, not 100%

Let's say you have three disability ratings: 50%, 30%, and 10%.

Simple addition would give you 90%, but VA math works differently:

  1. Start with the highest rating: 50%. You now have 50% remaining ability.
  2. Apply 30% to the remaining 50%: 30% × 50% = 15%. Combined value: 50% + 15% = 65%. Remaining ability: 35%.
  3. Apply 10% to the remaining 35%: 10% × 35% = 3.5%. Combined value: 65% + 3.5% = 68.5%.
  4. Round to nearest 10%: 68.5% rounds to 70%.
Waterfall diagram showing how VA math combines 50%, 30%, and 10% ratings to reach 68.5%, which rounds to 70% 50% 15% 3.5% 31.5% remaining 1st rating: 50% 30% × 50% = 15% 10% × 35% = 3.5% Combined: 68.5% → rounds to 70%

Your combined VA rating would be 70%, not 90%.

Try the calculator to see how VA math applies to your specific ratings.

The Bilateral Factor

The bilateral factor (38 CFR § 4.26) provides a small bonus when you have disabilities affecting both sides of the body — for example, both knees, both arms, or both legs.

How it works:

  1. Combine the bilateral disabilities using VA math.
  2. Add 10% of that combined value to itself.
  3. Use the adjusted value in the overall combination.

Example: Left knee 20% + Right knee 10%. Combined bilateral: 20% + (10% × 80%) = 28%. Bilateral factor: 28% × 10% = 2.8%. Adjusted value: 28% + 2.8% = 30.8% (used in overall combination, not rounded yet).

Diagram showing bilateral factor calculation: left knee 20% plus right knee 10% combined to 28%, plus 2.8% bilateral bonus equals 30.8% Left Knee 20% + Right Knee 10% VA Math Combined 28% Bilateral factor: 28% × 10% = +2.8% Adjusted value: 30.8%

Rounding Rules

The final combined value is rounded to the nearest 10%. The VA rounds .5 up:

  • 74% or lower rounds down to 70%
  • 75% or higher rounds up to 80%
Number line showing how 68.5% rounds down to 70% and where the 75% rounding boundary falls 60% 70% 75% boundary 80% 90% 68.5% → 70% Rounds down Rounds up

This rounding can make a significant difference in your monthly payment, especially at higher rating levels.

Why VA Math Matters

Understanding VA math helps you set realistic expectations for your combined rating and monthly compensation. It also helps you understand why pursuing additional claims may or may not significantly change your combined rating.

For example, if you already have a 90% combined rating, adding a 10% disability only increases your exact combined value by 1% (10% of the remaining 10%), resulting in the same rounded rating of 90%.

This content is for informational purposes only and does not constitute legal or medical advice. For personalized guidance, consult a VA-accredited VSO, attorney, or claims agent.