How this instrument works
A VA combined disability rating is not the sum of a veteran's individual ratings. The VA treats a body at 0% disability as having 100 units of overall efficiency, and each rating removes a share of whatever efficiency is left, not a share of the original 100. A first rating of 50% leaves 50 units standing; a second, unrelated rating of 30% then removes 30% of those remaining 50 units, not 30% of the original 100. That is why the formula multiplies the two undisabled fractions together — (100−r₁)(100−r₂)⁄100 — rather than subtracting the ratings from 100 in turn.
The raw result of that multiplication almost never lands on a clean multiple of 10, so VA regulation rounds it to the nearest 10 before it becomes a veteran's official combined rating — the figure printed on a rating decision letter and the one that determines the compensation tier. This instrument reproduces both steps: the exact raw value from the combined-ratings formula, and the rounded figure the VA actually pays against, so a veteran or a service officer can check a decision letter's arithmetic directly instead of reading it off the VA's printed lookup table.
What it does not do matters too. It handles exactly two ratings at a time and applies none of the adjustments the VA layers on top for specific situations — the bilateral factor for paired limbs, individual unemployability, or dependency add-ons. Those change the dollar compensation without changing the arithmetic shown here, so this figure is a rating, not a benefit amount.
- Enter the first condition's percentage in First disability rating, %.
- Enter the second condition's percentage in Second disability rating, %. Order doesn't affect the result.
- Check Raw combined value (before rounding) for the exact figure the multiplication produces.
- Read VA combined disability rating, % for the value rounded to the nearest 10, the number that sets the compensation tier.
Worked example — a 50% and a 30% rating
Take a veteran rated 50% for one condition and 30% for a second, unrelated one. Adding them by hand suggests 80%, but the VA starts from remaining, undisabled capacity: the first rating removes 50% of it, leaving 50 units, and the second rating then removes 30% of those 50 units, not 30% of the original 100. Working the formula gives 100 − (100−50)(100−30)⁄100 = 100 − (50)(70)⁄100 = 65 — the value this instrument reports as Raw combined value (before rounding).
That 65 is not the number on the rating decision letter. VA regulation rounds every combined value to the nearest whole 10, and 65 sits exactly between 60 and 70 — the VA's rounding convention sends a value ending in 5 upward, so 65 becomes 70. The instrument returns 70 as the VA combined disability rating, %, which is the figure that actually maps to a monthly compensation amount, not the 65 a veteran might land on by adding wrong or rounding the other way.
Questions
Why don't two disability ratings simply add together?
Because the VA treats each additional rating as removing a share of whatever function is left, not a slice of the original 100 percent. A 50% rating leaves 50 units of capacity standing; a second 30% rating removes 30% of that remaining 50, not 30% of the full 100. Adding the two percentages by hand overstates the result — this instrument applies the VA's actual multiplicative method instead.
Why does a raw value of 65 round up to 70 and not down to 60?
VA regulation rounds every combined value to the nearest 10, and treats a value ending exactly in 5 as rounding upward — the same convention used throughout the VA's published combined ratings table. A raw value of 64 would round down to 60; a raw value of 65 rounds up to 70.
Does the order I enter the two ratings in change the result?
No. The formula is symmetric — swapping First disability rating, % and Second disability rating, % produces the same raw combined value and the same rounded rating, because (100−r₁)(100−r₂) is unchanged when r₁ and r₂ trade places.
What if I have three or more disability ratings to combine?
This instrument combines exactly two ratings at a time. To add a third, treat the combined rating from the first pair as one input and the new rating as the other, working from the highest individual rating down to the lowest — the same order the VA's own combined ratings table specifies for multiple conditions.
Does a higher combined rating always mean proportionally higher pay?
Not proportionally. VA compensation tables step up in flatter increments as the rating rises, and separate factors like dependents, individual unemployability, or special monthly compensation change the dollar amount independent of the percentage shown here. This instrument computes only the rating, never a payment figure.
References
- U.S. Department of Veterans Affairs — About VA disability ratings
- eCFR — Title 38, Part 4.25, Combined ratings table
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.