Add up the impairments on a multi-part case and you’ll overshoot the real rating every time. California combines them instead, using the PDRS’s Combined Values Chart (CVC) — the last step before a rating becomes weeks and dollars. Here’s the logic, the formula, and the places it changes outcomes.
The idea: percentages of what’s left
A PD rating is a percentage of the whole person. If a spine injury takes 20%, the next impairment can only impair the 80% that remains. So a second 20% impairment takes 20% of the remainder — 16 points — and the total lands at 36, not 40. Stack as many impairments as you like; the total approaches but never reaches 100%.
Reference combinations
A few anchors worth knowing cold (every value below is computed by the same engine that runs the calculator):
| A | B | Combined | Added would be |
|---|---|---|---|
| 10 | 10 | 19 | 20 |
| 20 | 20 | 36 | 40 |
| 25 | 15 | 36 | 40 |
| 30 | 20 | 44 | 50 |
| 40 | 40 | 64 | 80 |
| 50 | 40 | 70 | 90 |
| 50 | 50 | 75 | 100 |
| 70 | 30 | 79 | 100 |
Three or more impairments
With several body parts, the finals are folded pairwise, largest first — combine the two biggest, combine the result with the next, and so on, rounding at every step. The sample case’s 18% shoulder, 11% spine, and 7% neck fold as 18 C 11 = 27, then 27 C 7 = 32% PD. Because of the per-step rounding, a different order can occasionally land a point off — largest-first is the canonical PDRS order.
The same-limb wrinkle
Two impairments to the same arm don’t go straight to the whole-person chart. They’re first combined on the extremity’s own scale, capped at the value of amputating that limb, and then converted to whole-person terms — a limb can never rate worse than its loss. Multi-region cases therefore combine at two levels: within the extremity, then across the body.
Why one point at the top matters so much
The CVC decides which side of a statutory threshold a case lands on, and the thresholds are cliffs, not slopes:
70% PD = 433.25 weeks × $290 = $125,642.50 — plus a life pension: a weekly check that continues for the rest of the worker’s life (Lab. Code §4659).
50 C 40 combines to exactly 70. Whether a disputed body part survives is the whole ballgame.
The same cliff logic applies at 100% (permanent total disability, lifetime indemnity at the TD rate). When a case sits near a threshold, test the disputed impairment both ways in the calculator — the scenario compare shows what each contested point is actually worth.