VA Math Made Simple: How Multiple Disability Ratings Combine

One of the most confusing parts of VA disability compensation is the way VA combines multiple disability ratings.

A Veteran may look at several service-connected conditions and think:

50% + 30% + 20% = 100%

But VA does not calculate combined ratings that way.

VA uses what is often called VA math. The official idea behind it is sometimes called the whole person theory. In plain English, VA starts with the idea that a person is 100% efficient, then each disability reduces what is left.

That is why multiple ratings usually do not add up the way Veterans expect.

The easiest way to understand VA math

Think of your body as a full glass of water.

At the beginning, the glass is 100% full.

If VA grants a 50% rating, VA treats that as taking away half of the full glass. That leaves 50% remaining.

If VA then grants a 30% rating, VA does not take 30% from the original full glass. It takes 30% from what is left.

So:

Start with 100%
A 50% disability leaves 50% remaining
A 30% disability takes 30% of the remaining 50%
30% of 50 is 15
50 + 15 = 65
VA rounds 65 to 70

So a 50% rating and a 30% rating combine to 70%, not 80%.

That is the basic idea.

Why VA does not simply add the percentages

VA’s system is designed so that a Veteran cannot be more than 100% disabled under the regular rating schedule.

That is why each new rating is applied to the remaining “un-disabled” portion of the Veteran.

For example:

A 60% rating means VA considers the Veteran 40% efficient
A later 30% rating is applied to that remaining 40%
30% of 40 is 12
60 + 12 = 72
VA rounds 72 to 70

This is why a Veteran can have many ratings and still not reach 100%.

It can feel unfair or confusing, but it is how the combined ratings table works.

Use the “what is left” method

Here is the simple rule:

Each new rating applies only to what is left.

If you remember nothing else, remember that.

VA starts with the highest rating first, then combines the next highest rating, then the next, and so on.

For example, assume a Veteran has:

VA does not add them to get 110%.

Instead:

Start with the 60% rating. That leaves 40% remaining.

Apply the 30% rating to the remaining 40%. 30% of 40 is 12. 60 + 12 = 72.

Apply the 20% rating to what remains after 72%. If the Veteran is 72% disabled, then 28% remains. 20% of 28 is 5.6. 72 + 5.6 = 77.6.

VA rounds according to the combined ratings rules. The final combined rating would generally round to 80%.

This is not the exact way VA’s table is displayed, but it is a helpful way to understand what the table is doing.

The ratings are combined from highest to lowest

VA generally starts with the highest disability rating and works downward.

That matters because the largest disability is applied first to the full 100% person. Smaller disabilities are then applied to what remains.

For example, a Veteran with 70%, 30%, and 10% would generally be combined in this order:

This is why Veterans should be careful when trying to estimate a combined rating. The order matters, and the table matters.

Examples that surprise Veterans

Example 1: 10% + 10%

Many Veterans assume:

10 + 10 = 20

But under VA math, two 10% ratings combine to 19%, which rounds to 20%.

That one ends up looking normal after rounding, but the unrounded number is still 19.

Example 2: 50% + 50%

Many Veterans assume:

50 + 50 = 100

But VA math works differently:

First 50% leaves 50% remaining
Second 50% applies to the remaining 50%
50% of 50 is 25
50 + 25 = 75
75 rounds to 80

So two 50% ratings usually combine to 80%, not 100%.

Example 3: 70% + 30%

Many Veterans assume:

70 + 30 = 100

But:

70% leaves 30% remaining
30% of 30 is 9
70 + 9 = 79
79 rounds to 80

So 70% and 30% usually combine to 80%, not 100%.

Example 4: 90% + 10%

Many Veterans assume a 10% rating should move them from 90% to 100%.

But:

90% leaves 10% remaining
10% of 10 is 1
90 + 1 = 91
91 rounds back to 90

So adding a 10% rating to a 90% combined rating may not change the final monthly payment at all.

That can be frustrating, but it is a common result of VA math.

Why it gets harder near 100%

The closer a Veteran gets to 100%, the harder it becomes to move the combined rating higher.

That is because there is less “remaining efficiency” left for the next rating to affect.

For example:

At 50%, there is still 50% left
At 70%, there is still 30% left
At 90%, there is only 10% left

A 10% rating applied to a remaining 10% only adds 1 point before rounding.

That is why a Veteran at 90% may need a significant new rating, or several additional ratings, to reach 100% schedular.

The difference between 90% and 100% can be large

The difference between a 90% combined rating and a 100% combined rating can be significant.

It can affect:

Monthly compensation
Access to additional benefits
State benefits
Dependent benefits
Health care considerations
Eligibility for certain programs
Whether TDIU should be considered

Veterans who are close to 100% should carefully review whether VA rated each condition correctly.

Sometimes the issue is not “VA math.” Sometimes the issue is that VA assigned the wrong rating, overlooked a condition, failed to grant secondary service connection, or missed evidence that supports a higher evaluation.

What about the bilateral factor?

VA math can become more complicated when the bilateral factor applies.

The bilateral factor may apply when a Veteran has compensable disabilities affecting both arms, both legs, or paired skeletal muscles.

For example, if a Veteran has a service-connected right knee condition and a service-connected left knee condition, the bilateral factor may need to be considered before the final combined rating is calculated.

The bilateral factor can sometimes make a meaningful difference, especially when a Veteran has multiple conditions involving both lower extremities or both upper extremities.

This article focuses on the basic combined-rating concept. If both sides of the body are involved, Veterans should be careful because the calculation may not be as simple as using the basic combined ratings table.

Combined rating is different from individual ratings

A Veteran’s individual ratings remain important even when the combined rating does not change.

For example, a new 10% rating may not move a Veteran from 90% to 100%. But that 10% rating may still matter because it:

Establishes service connection
Could support secondary claims
Could affect future increases
Could contribute to the bilateral factor
Could matter if another rating later increases
Could help support TDIU in the right case
Could affect eligibility for some benefits or health care issues

Do not assume a rating is worthless just because it does not immediately change the combined percentage.

Why Veterans should check the actual VA decision

Veterans should always review the VA rating decision carefully.

Look for:

Each condition VA granted
Each percentage assigned
Each effective date
Whether VA denied any claimed conditions
Whether VA failed to address secondary conditions
Whether VA missed favorable evidence
Whether VA applied the bilateral factor
Whether the combined rating makes sense
Whether TDIU was reasonably raised

The combined rating is only the final number. The important work is often hidden in the individual ratings and the reasons VA gave for each decision.

When VA math may point to an appeal issue

VA math itself is usually mechanical. The bigger issue is whether VA used the right inputs.

A Veteran may need to challenge the decision if VA:

Rated a condition too low
Denied a condition that should be service connected
Ignored symptoms that support a higher rating
Failed to consider flare-ups
Relied on an inadequate C&P exam
Failed to consider functional loss
Missed secondary service connection
Failed to apply the bilateral factor
Used the wrong effective date
Failed to consider TDIU

In other words, the combined rating may be correct based on the ratings VA assigned, but the assigned ratings themselves may be wrong.

A simple way to think about it

Here is the easiest summary:

VA does not add disabilities. VA subtracts each disability from what is left of the whole person.

So instead of thinking:

50 + 30 = 80

Think:

50 leaves 50. Then 30% of the remaining 50 adds 15. That equals 65, which rounds to 70.

That is VA math.

Bottom line

VA combined ratings are confusing because they do not work like normal addition.

The key idea is the whole person theory. VA starts with the highest rating, applies each additional rating to what remains, then rounds the final combined value to the nearest 10%.

This can explain why a Veteran with several service-connected disabilities may have a lower combined rating than expected.

But Veterans should not stop at the math. The real question is whether VA assigned the correct ratings in the first place.

If VA underrated a condition, denied a valid claim, missed secondary service connection, failed to apply the bilateral factor, or ignored how the disabilities affect work and daily life, the Veteran may have appeal options.

A confusing combined rating may be the start of the review, not the end of the story.

This article is for general information only and is not legal advice. Reading this article or contacting our office does not create an attorney-client relationship unless we agree to representation in writing.