One of the most confusing aspects of VA disability is how ratings combine. Many veterans are shocked to learn that 50% + 30% doesn't equal 80%—it equals 65% (rounded to 70%). This guide explains exactly how "VA math" works.
Why VA Doesn't Just Add Ratings
VA uses the "whole person theory" established in 38 CFR § 4.25. The idea is that you start as a "whole" (100%) person, and each disability takes away a percentage of your remaining health—not your total health.
The VA Math Formula
Here's how to calculate combined ratings step-by-step:
Step 1: Convert to Decimal and Calculate "Efficient" Percentage
For each rating, calculate what percentage of your "remaining efficiency" is lost:
- Start at 100 (whole person)
- Subtract first rating → this is your "remaining efficiency"
- Apply next rating to remaining efficiency
- Continue for all ratings
Example: 50% + 30% + 20%
| Rating | VA Criteria |
|---|---|
| Start | 100% (whole person) |
| First 50% | 100 - 50 = 50% remaining efficiency |
| Second 30% | 30% of 50 = 15. New total: 50 + 15 = 65% disabled |
| Third 20% | 20% of remaining 35% = 7. New total: 65 + 7 = 72% disabled |
| Final | 72% rounds to 70% (VA rounds to nearest 10) |
Using regular math: 50 + 30 + 20 = 100%
Using VA math: 72%, rounded to 70%
VA Rounding Rules
After combining all ratings, VA rounds to the nearest 10%:
- 0.5 or higher → rounds UP (e.g., 75% → 80%, 85% → 90%)
- Below 0.5 → rounds DOWN (e.g., 74% → 70%, 84% → 80%)
Order of Calculation
VA always calculates ratings from highest to lowest. This is required by 38 CFR § 4.25 and actually benefits veterans because applying the highest rating first means you lose the largest percentage from 100%, not from a reduced number.
Example: Why Order Matters
Ratings: 70%, 20%, 10%
- Start: 100%
- Apply 70%: 100 - 70 = 30% remaining
- Apply 20%: 20% of 30 = 6%. Total disabled: 76%
- Apply 10%: 10% of 24 = 2.4%. Total disabled: 78.4%
- Rounded: 80%
The Bilateral Factor
The bilateral factor is a 10% bonus applied when you have the same condition affecting both sides of your body (both knees, both arms, etc.).
How the Bilateral Factor Works:
- Identify all bilateral conditions (affecting paired extremities)
- Combine just the bilateral ratings using VA math
- Add 10% of that combined bilateral total
- Then combine with remaining non-bilateral ratings
Bilateral Factor Example:
Veteran has: Left knee 20%, Right knee 10%, PTSD 50%
| Rating | VA Criteria |
|---|---|
| Step 1 | Combine bilateral: 20% + 10% = 28% (VA math) |
| Step 2 | Add 10% bonus: 28 × 0.10 = 2.8. Total bilateral: 30.8% |
| Step 3 | Combine with PTSD 50%: 50 + (50 × 0.308) = 65.4% |
| Final | 65.4% rounds to 70% |
Without bilateral factor, the same ratings would combine to only 64% (rounded to 60%).
Reaching Key Thresholds
Certain combined ratings unlock additional benefits:
| Rating | VA Criteria |
|---|---|
| 30%+ | Additional compensation for dependents (spouse, children) |
| 40%+ | Qualifies for one TDIU pathway (with one 60%+ rating) |
| 70%+ | Qualifies for TDIU (with at least one 40%+ rating) |
| 100% | Maximum compensation; may qualify for SMC benefits |
Use Our Calculator
Don't do this math by hand—use our VA Disability Calculator. It automatically:
- Applies VA math correctly
- Orders ratings from highest to lowest
- Detects and applies the bilateral factor
- Shows 2026 compensation amounts
- Calculates dependent add-ons
Why Understanding VA Math Matters
- Realistic expectations: Know what combined rating to expect before filing
- Strategic claims: Understand which additional claims will push you to next threshold
- Catch errors: If your rating letter math doesn't match, you can appeal
- Bilateral conditions: Don't miss the 10% bonus—claim both sides