The single most confusing thing about VA disability ratings is the combined math. If you have a 50% rating for one condition and another 50% rating for a second condition, your combined rating is not 100%. It is 75%. The VA uses a specific formula — sometimes called “VA math” — that treats each subsequent rating as a percentage of the remaining unrated capacity, not as additive to the prior rating. This guide walks through how VA combined ratings actually work, what specific conditions tend to rate, the bilateral factor, and how to check the VA’s math against your situation.
For background on filing an initial claim and what each rating means in terms of monthly compensation, see VA disability benefits 101.
How VA Math Actually Works
The VA combined rating formula treats each disability as reducing your remaining “healthy” capacity, not as additive to other disabilities. The math:
- Start at 100% healthy.
- Apply the highest rating first. A 50% rating reduces healthy capacity to 50%.
- Apply each subsequent rating as a percentage of the remaining capacity. A second 50% rating reduces the remaining 50% by half, leaving 25% healthy capacity. So combined rating is 100% − 25% = 75%.
- Continue with each subsequent rating in descending order.
- Round the final result to the nearest 10%.
The practical effect: ratings stack diminishingly. Once you’re above about 70% combined, adding more lower ratings barely moves the needle. Once you’re at 80%, getting to 90% requires substantial additional ratings.
Woobie’s VA disability calculator does the math for you with your specific ratings entered. The VA Math category covers the rules in further depth across 36 posts.
Why This Matters Strategically
The combined rating math has several practical consequences worth understanding:
- The first major rating matters most. Going from 0% to 50% (no other ratings) takes you straight to 50%. Going from 50% to 100% (single condition) requires substantially more severity documented.
- Stacking small ratings has diminishing returns. Adding a 10% rating to a 70% combined rating barely changes your final number after rounding.
- The order doesn’t change the final answer. The math is commutative — the same set of ratings always produces the same combined rating regardless of which you list first.
- Bilateral conditions get a 10% bonus. Conditions affecting both sides of the body (both knees, both shoulders, both hands) get a 10% bilateral factor added before final combining. This is one of the few ways to boost the math.
- 100% combined ≠ 100% individual. A combined 100% (with multiple ratings) is treated differently in some VA contexts than a single 100% rating (often called “100% schedular” or “100% individual”). The benefits are mostly the same but a few specific programs treat them differently.
Common Conditions and Their Typical Ratings
Tinnitus
Capped at 10% under current rules, regardless of severity. One of the most commonly claimed conditions because the documentation requirement is straightforward (audiometric testing + lay statements about ringing).
Hearing Loss
Rated 0% to 100% based on a table that combines puretone threshold averages and speech discrimination scores from audiometric testing. Most service-connected hearing loss rates 0% or 10%, but severe cases can reach much higher.
Sleep Apnea
Four tiers under 38 CFR Part 4: 0% (mild without CPAP), 30% (mild with CPAP), 50% (moderate with CPAP-dependent), 100% (severe with significant residuals). Sleep apnea rating criteria are under active review and may change; check current rules. Service connection often relies on documented in-service sleep complaints or secondary connection to other conditions (PTSD, weight gain from medication, etc.).
PTSD and Other Mental Health
Rated 0%, 10%, 30%, 50%, 70%, or 100% based on the level of occupational and social impairment documented. The C&P examiner’s assessment of how your symptoms affect work and relationships drives the rating. Documentation of frequency, severity, and specific functional impacts (missing work, social withdrawal, relationship damage, suicidal ideation, hospitalization) is essential.
Musculoskeletal Conditions
Back, knee, shoulder, hip, ankle, and other joint conditions rate based on range of motion, painful motion, instability, and functional impact. Most musculoskeletal conditions rate 10% or 20% on a single joint; severe limitation can rate 40% or higher. Multiple joints quickly stack with the bilateral factor.
Migraines
0%, 10%, 30%, or 50% based on frequency and severity of “prostrating attacks” (the VA’s term for migraines severe enough to require lying down in a dark room and stopping normal activity). Documentation of frequency is critical.
Scars
Rated based on size, location, and whether they are painful, unstable, or limit motion. Most scars rate 0% or 10% individually.
Diabetes Type II (Agent Orange Presumptive)
20% to 100% based on the level of medical management required and complications. Presumptive for Agent Orange-exposed Vietnam veterans.
GERD and Other Gastrointestinal
Rates from 10% to 60% based on symptom severity and dietary impact. Frequently connected as secondary to medications taken for other service-connected conditions.
The Bilateral Factor
One of the few ways to genuinely boost a combined rating. If you have service-connected disabilities affecting both sides of the body (both knees, both shoulders, both hands, etc.), the VA adds a 10% bonus to the combined rating of those bilateral conditions before combining with other ratings.
Example: 20% right knee + 20% left knee. Combined for bilateral purposes: 36% (using VA math, then adding 10% bilateral factor). This is then combined with any other ratings normally.
The bilateral factor is sometimes missed by VA raters. Worth checking the math against your decision letter if you have bilateral conditions.
Secondary Service Connection
A condition can be service-connected because it is caused by, or aggravated by, an already service-connected condition. This is called secondary service connection, and it is one of the most underused paths to additional ratings.
Examples of common secondary connections:
- GERD secondary to PTSD (or to NSAIDs taken for service-connected musculoskeletal pain)
- Sleep apnea secondary to PTSD or weight gain from medication
- Depression secondary to chronic pain conditions
- Hypertension secondary to PTSD
- Erectile dysfunction secondary to medications
- Bilateral plantar fasciitis secondary to altered gait from a knee injury
Each secondary connection requires its own medical nexus opinion linking the secondary condition to the primary service-connected one. Worth pursuing when you have multiple symptoms developing in sequence after your primary service-connected condition.
The 2026 VA Updates
Specific rating criteria evolve. The VA periodically updates portions of 38 CFR Part 4. Recent and pending updates include changes to mental health rating criteria, evolution of presumptive conditions under the PACT Act, and refinement of specific rating tables. Woobie’s 2026 VA Updates category covers current changes.
How to Check the VA’s Math
- Pull your decision letter listing each rated condition and percentage.
- List the ratings in descending order.
- Apply the VA combined formula (or use Woobie’s calculator).
- Apply the bilateral factor if applicable.
- Compare your math to the VA’s combined rating on the decision letter.
If the math doesn’t match — which happens more often than you’d think — that’s grounds for a clear-and-unmistakable-error claim or supplemental claim. See VA appeals and supplemental claims for the path forward.
Frequently Asked Questions
If I have a 50% rating and another 30% rating, what’s my combined rating?
65%, rounded to 70%. Math: 100 − 50 = 50 remaining; 30% of 50 = 15; 50 + 15 = 65; rounds to 70%.
Can I get to 100% with multiple ratings?
Yes — combined 100% is achievable through stacking multiple ratings. Going from 90% to combined 100% is the hardest stretch because of the diminishing-returns math, but it’s achievable with enough bilateral and high-impact ratings.
What is TDIU and how is it different from 100% schedular?
Total Disability Individual Unemployability (TDIU) pays at the 100% compensation rate even if your combined rating is less than 100%, provided you can document that your service-connected conditions prevent you from maintaining substantially gainful employment. TDIU has specific requirements; see Woobie’s TDIU coverage.
Do I get the bilateral factor automatically?
The VA is supposed to apply it automatically when you have bilateral conditions, but it sometimes gets missed in the math. Worth checking against your decision letter.
What about smoothing ratings — can the VA reduce my rating?
Yes, the VA can propose to reduce a rating if your condition is documented to have improved. There are specific procedures and protections. “Protected” ratings (those held for specific durations) have additional protections against reduction.
How do I use Woobie to check my ratings?
Use Woobie’s disability calculator to enter your ratings and see the combined math, then compare against your VA decision letter. The Claims Accelerator walks through specific condition-by-condition rating questions.
Check Your Ratings
Use the disability calculator, browse the VA Math articles, or apply to start with Claims Accelerator for a structured walkthrough of your specific situation.