How to Calculate VA Combined Ratings Manually

The VA's combined ratings formula is one of the most-misunderstood pieces of disability law. Most veterans never learn how to calculate it themselves, which means most veterans cannot verify what the VA is paying them. This guide changes that. By the time you finish reading, you'll be able to combine any number of ratings using nothing but pen and paper, verify any VA decision letter, and spot calculation errors that often cost veterans hundreds of dollars per month.

The formula is in 38 CFR § 4.25 and it's simpler than it looks. We'll walk through it from scratch, work multiple examples by hand, and cover the bilateral factor, the rounding rule, mental math shortcuts, and the common mistakes that defeat manual calculations.

01
Why Learn Manual Calculation

Online calculators are useful, but they're black boxes. Manual calculation gives you something a calculator can't: understanding. When you can do the math yourself, you can:

• Verify your VA decision letter without depending on any tool
• Spot errors the VA made — especially missing bilateral factor
• Predict the impact of a new secondary claim before filing
• Understand why a small rating might push you over a rounding boundary
• Make better strategic decisions about which claims to pursue
• Explain VA math to family, friends, and other veterans

Manual calculation also reveals the underlying logic — once you see why each successive condition contributes less, the whole VA system starts to make sense.

02
The Core Formula Explained Simply

The combined ratings formula in 38 CFR § 4.25 is:

In plain English: "Take the higher rating. Then add a portion of the next rating — the portion being how much healthy capacity remains."

The intuition: a healthy person has 100% functional capacity. Each disability reduces that remaining capacity by its percentage. After a 50% disability, you have 50% capacity left. The next 30% disability eats 30% of that remaining 50%, which is 15. So total disability is 50 + 15 = 65%.

03
Worked Example — Two Conditions

Scenario: Veteran has PTSD at 50% and sleep apnea at 30%. What's the combined rating?

Result: combined rating is 70%. Not 80% as simple addition would suggest.

04
Worked Example — Three Conditions

Scenario: Veteran has PTSD at 70%, back at 40%, and tinnitus at 10%. Combined rating?

05
Worked Example — Many Conditions

Scenario: Veteran has PTSD 70%, sleep apnea 50%, back 20%, knee 10%, tinnitus 10%, hypertension 10%.

• Ranked: 70, 50, 20, 10, 10, 10
• 70 + 50 → 70 + 50 × 30/100 = 70 + 15 = 85%
• 85 + 20 → 85 + 20 × 15/100 = 85 + 3 = 88%
• 88 + 10 → 88 + 10 × 12/100 = 88 + 1.2 = 89.2%
• 89.2 + 10 → 89.2 + 10 × 10.8/100 = 89.2 + 1.08 = 90.28%
• 90.28 + 10 → 90.28 + 10 × 9.72/100 = 90.28 + 0.972 = 91.25%
• Round 91.25 → 90%

Six conditions totaling 170% in simple addition only combine to 91.25%, rounded to 90%. Each successive condition contributes less than the previous one.

06
Adding the Bilateral Factor

Under 38 CFR § 4.26, when ratings affect paired extremities (both arms, both legs, or one arm + one leg), add a 10% bilateral factor to those combined ratings before combining with other conditions.

Step-by-Step Bilateral Application

1. Identify which conditions affect paired extremities
2. Combine those paired-extremity ratings using the standard formula
3. Multiply that combined result by 10% (i.e., 0.10)
4. Add the bilateral factor to the paired-extremity combined
5. Combine this adjusted total with all other (non-bilateral) ratings

Worked Bilateral Example

Scenario: 30% right knee + 20% left knee + 50% PTSD

• Combine knees: 30 + 20 × 70/100 = 30 + 14 = 44%
• Bilateral factor: 44 × 0.10 = 4.4%
• Adjusted knee total: 44 + 4.4 = 48.4%
• Combine with PTSD: 50 + 48.4 × 50/100 = 50 + 24.2 = 74.2%
• Round 74.2 → 70%

Without bilateral factor, the same conditions combine to 50 + 44 × 50/100 = 72%, still rounded to 70%. In this scenario the bilateral factor doesn't change the rounded outcome — but in close cases (e.g., a pre-round value of 64% becoming 65%), it can be the difference between two rating tiers.

07
The Rounding Rule

Under 38 CFR § 4.25(a), round to the nearest 10% — and ONLY at the very end. Never round intermediate values.

The 95 → 100 boundary is particularly valuable. Many veterans reach the 100% schedular rate by accumulating to 95%+ pre-round, not by hitting 100% exactly.

08
Mental Math Shortcuts

You can do most combined rating calculations in your head with these shortcuts:

• For 10% additions: "remaining ÷ 10" gives the addition (10 of 50 remaining = 5)
• For 20% additions: "remaining × 2 ÷ 10" (20 of 50 = 10)
• For 30% additions: "remaining × 3 ÷ 10" (30 of 50 = 15)
• For 50% additions: "remaining ÷ 2" (50 of 50 = 25)
• Remaining after rating X = 100 − X (after 70%, remaining = 30)
• Two equal ratings: X + X always combines to less than 2X — calculate the second addition as X × (100 − X) / 100

Quick Reference: Common Combinations

• 10% + 10% = 19% → 20%
• 20% + 20% = 36% → 40%
• 30% + 30% = 51% → 50%
• 50% + 30% = 65% → 70%
• 50% + 50% = 75% → 80%
• 70% + 30% = 79% → 80%
• 70% + 50% = 85% → 90%

09
Using the Combined Ratings Table

Alternative to the formula: 38 CFR § 4.25 provides a lookup table. Find one rating along the top row and another along the side; the intersection is the combined value.

To use the table for many conditions:

1. Look up the combined of the top two ratings
2. Use that result and look up against the third rating
3. Continue until all ratings are combined

The formula and table produce the same answer. The table is faster if you can find a copy (printed in 38 CFR or online); the formula is more flexible because it doesn't require lookup.

10
Verifying a VA Decision Letter

11
Common Manual Calculation Mistakes

• Adding ratings as simple sums — the most common mistake. 50% + 30% does NOT equal 80%.
• Wrong order of operations — applying the formula in non-decreasing order produces different intermediate values (final answer is mathematically the same, but easier to track in order).
• Rounding too early — rounding intermediate values changes the final outcome. Only round once, at the very end.
• Forgetting the bilateral factor — paired-extremity conditions need the 10% bonus before combining with others.
• Confusing the bilateral factor formula — multiply by 0.10 of the combined paired total, then add. Don't multiply by 1.10 and round.
• Missing SMC stacking rules — SMC-K ($136.06) adds on top of combined rating-based pay, but isn't part of combined rating math.
• Counting non-service-connected conditions — only service-connected conditions go into the formula.

12
Frequently Asked Questions

VA Claims US Editorial Team

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The VA Claims US editorial team is dedicated to helping veterans and their families understand and navigate the VA disability system. Our content is reviewed for accuracy against current VA regulations and updated whenever rates or policies change. Have a question? Contact us here.