VA Math Guide

Why VA Math is not adding — 38 CFR §4.25 explained

Every veteran has hit this wall: you have two 50% ratings, you expect 100%, the letter says 80%. Or you have ratings of 70, 50, 30, 30, 10, 10 — and the VA gives you 90% combined. The math is correct. It's the formula that's confusing.

The §4.25 "efficiency" formula

VA treats your body as 100% efficient at baseline. Your first (highest) disability reduces that efficiency. The next disability reduces the remaining efficiency — not the original 100%. The pattern repeats for every disability.

Example A — two 50% ratings:

• Start: 100% efficient.
• First 50% disability → 50% remaining.
• Second 50% reduces that remaining 50% by half → 25% reduction.
• Total disability: 50% + 25% = 75%.
• Round to nearest 10% → 80% combined.

Example B — 70%, 50%, 30%, 30%, 10%, 10% (always sort highest first):

• After 70%: efficiency = 30%.
• + 50% of 30% = 15% more → 85% total → efficiency 15%.
• + 30% of 15% = 4.5% → 89.5% → efficiency 10.5%.
• + 30% of 10.5% = 3.15% → 92.65% → efficiency 7.35%.
• + 10% of 7.35% = 0.735% → 93.39%.
• + 10% of 6.62% = 0.66% → 94.05%.
• Round to nearest 10% → 90% combined.

The rounding rule (the part many calculators get wrong)

Round to the nearest 10% only at the very end. 65% rounds up to 70%; 64% rounds down to 60%. Never round intermediate steps. Calculators that round at each step give the wrong final answer for some combinations.

What about the bilateral factor?

If you have ratings of both arms or both legs (or paired skeletal muscles), 38 CFR §4.26 adds a 10% bonus on top of the combined sub-total for that pair, BEFORE folding into the rest. The bonus can push your final rating up by a full tier. See our bilateral factor guide.

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