Every workers’ comp case that involves permanent injury ends with a number — your impairment rating. It’s a percentage, usually between 0% and 100%, that’s supposed to capture how much your body is permanently worse off than before the injury. That percentage, more than anything else, determines what your case is worth. Here’s how the number gets made, and what to do if the one you got is too low.
The starting point: Maximum Medical Improvement
You can’t get a permanent rating until your doctor decides you’ve hit Maximum Medical Improvement (MMI), sometimes called Permanent and Stationary (P&S) status in California. MMI doesn’t mean you’re back to normal — it means you’re as healed as further treatment is likely to make you in the next 12 months.
MMI is a doctor’s judgment call, and it’s often contested. Carriers push for early MMI because once you reach it, temporary disability benefits typically end. Workers and their treating doctors sometimes resist because more treatment — surgery, injections, extended PT — could improve function. If your treating doctor says MMI and you don’t feel done, a QME evaluation can be requested to challenge it.
The rating book: AMA Guides 5th vs 6th edition
Once you’re at MMI, a doctor (treating physician, QME, or AME) assigns an impairment rating using the AMA Guides to the Evaluation of Permanent Impairment. There are two editions in active use:
- 5th edition (2001). Still used in California for all dates of injury, and in a handful of other states. Generally produces higher ratings for the same injury than the 6th.
- 6th edition (2008). Used in Texas, Florida, Tennessee, and the majority of states. Adopts a diagnosis-based approach with explicit grade modifiers and, for many soft-tissue injuries, produces lower ratings than the 5th.
New York doesn’t use the AMA Guides at all for non-schedule loss — it has its own state-specific impairment guidelines. A handful of other states use hybrid approaches. Which edition applies to your case is determined by state law and the date of injury, not by the doctor’s preference.
Whole-person vs body-part ratings
Two formats come up:
- Whole-person impairment (WPI). A single percentage representing total bodily impairment. California, Texas, and most 6th-edition states use this.
- Scheduled body-part impairment. Many eastern states (New York, Pennsylvania, New Jersey, parts of Florida for specific injuries) use scheduled weeks of benefits per body part — e.g., losing a hand might equal 244 weeks of benefits in New York regardless of your occupation.
The body part matters too. A 10% WPI to the spine pays differently than a 10% WPI to the knee in some states, because the rating gets adjusted by occupation and earning capacity.
How the rating becomes a dollar amount
This is where state law diverges sharply.
California uses the most complex formula. A QME assigns a WPI percentage. That gets adjusted by:
- A future earning capacity (FEC) modifier (about 1.4x for most injuries since 2013)
- An occupation adjustment (heavy-duty workers get a boost)
- An age adjustment (older workers usually get a small boost)
The resulting permanent disability percentage is then multiplied by a fixed dollar amount per percentage point — scaled by your average weekly wage with statutory minimums and maximums. For 2026 California dates of injury, a 20% permanent disability roughly equals $30,000 to $40,000 in cash; 50% permanent disability roughly equals $115,000 to $135,000. Above 70%, you may qualify for lifetime weekly payments instead of a lump sum.
Texas uses a much simpler formula: WPI rating × 3 weeks of impairment income benefits per percentage point, paid at 70% of your average weekly wage (capped at the state maximum). A 15% WPI = 45 weeks of payments.
Florida uses impairment benefits at 75% of your TTD rate, paid for a number of weeks tied to the impairment percentage (2 weeks per percentage point for the first 10%, escalating from there).
New York uses scheduled loss for extremities (set numbers of weeks per body part) plus a separate non-scheduled framework for back, neck, and systemic injuries based on loss of wage-earning capacity.
See our benefit-amount guide for the underlying wage-replacement math.
Why ratings get disputed
A few percentage points routinely mean tens of thousands of dollars, so neither side accepts a number without scrutiny. Common disputes:
- Range of motion measurements. The 5th edition relies heavily on ROM. If the doctor measured on a good day, your rating is low. If on a bad day, it’s high. Re-measurement on a different day often changes the number.
- Diagnosis category. Under the 6th edition, the rating starts from a diagnosis class. Whether your herniation is “Class 1” or “Class 2” can mean a 5% vs 13% rating.
- Grade modifiers. The 6th edition has three grade modifiers (functional history, exam findings, clinical studies). A point in either direction shifts the percentage.
- Psych overlay. Many physical injuries generate genuine secondary depression or anxiety. Whether that gets its own rating is constantly contested.
How to challenge a low rating
If the rating you got feels too low, you have options:
- Ask your treating doctor for a re-rating. If your treating physician issued the rating, request a supplemental report explaining the methodology. Sometimes the doctor simply missed a body part or under-rated a measurement.
- Request a QME. If you’re unrepresented or your attorney hasn’t already, the panel-QME process produces an independent rating. See our QME explainer for how that works.
- Use an AME if represented. If both sides have counsel and an AME is acceptable, this is often faster. The tradeoff is described in our QME vs AME post.
- Continue treatment. If you’re not actually at MMI, your true rating can’t be measured yet. Surgery, injection series, or a structured PT block may change the picture.
- Depose the rating doctor. An applicant’s attorney can take the rating doctor’s deposition and pin down weaknesses in the methodology. Reports often don’t survive cross-examination.
Apportionment: when prior conditions cut the rating
Apportionment is the rule that says you don’t get paid for the part of your impairment that wasn’t caused by this work injury. If you had degenerative disc disease before you lifted the box at work, the doctor is supposed to apportion: maybe 60% of your current 20% WPI is from the work injury, and 40% is pre-existing. Only the 60% counts.
States vary on how aggressively this is applied. California allows apportionment to non-industrial causation but requires the doctor to support it with specific medical reasoning, not just “age and degeneration.” A boilerplate apportionment finding is challengeable. New York largely rejects apportionment for permanent injury claims. Florida and Texas fall in between.
If your rating got slashed by apportionment, the question to ask is: what specific medical reasoning supports the percentages? If the report just asserts a 50/50 split without citing imaging, history, or prior records, it’s vulnerable on appeal.
What to do with your rating
Once the rating is final, the carrier will usually make a settlement offer. Don’t accept the first one. Most carriers open at 50% to 70% of full case value. Our settlement guide walks through the negotiation. If your claim was denied outright before you ever got to a rating, start with the denial-appeal guide.
Above all: don’t sign a Compromise & Release or equivalent final settlement document before you understand the rating, the apportionment, and the future medical treatment your number is supposed to cover. Once you sign, the case is closed — even if the rating turns out to have been wrong. A workers’ comp attorney can review the rating and the settlement number for a free consultation in most states, and broader background sits in the WC FAQ and MPN hub.