The multiplier method: scaling off your damages
The multiplier method is the industry's default approach. It takes your economic damages — medical bills and lost wages — and multiplies that total by a factor generally between 1.5 and 5, chosen based on injury severity, recovery time, and whether any permanent impairment is involved.
The per diem method: valuing each day
The per diem (Latin for "per day") method works differently. It assigns a specific dollar value to a single day of pain and suffering and multiplies that rate by the total number of days of documented recovery, tying the value directly to time rather than to the size of your medical bills.
Why "catastrophic" matters more than the method in a malpractice claim
For an ordinary Missouri personal injury case, neither method runs into a cap at all. Medical malpractice is different, and here the decisive factor usually isn't which valuation method was used — it's whether the injury meets the statutory definition of "catastrophic" under RSMo § 538.205. The two tiers of Missouri's malpractice cap sit roughly $360,000 apart, so classifying an injury correctly changes the applicable ceiling far more than any reasonable difference between the multiplier and per diem outputs would.
So identifying the injury tier matters more than the method
Before investing effort in choosing between the multiplier and per diem methods for a Missouri malpractice claim, it's worth establishing whether the injury involves quadriplegia, paraplegia, loss of two or more limbs, significant permanent cognitive impairment, irreversible major organ failure, significant vision loss, or another injury a court would find catastrophic given its severity and permanence. That classification can matter more to the final number than either valuation method.
Neither is required by Missouri law
Both methods remain negotiating tools, not a formula Missouri courts are required to apply. A jury retains discretion to award whatever amount it finds appropriate for noneconomic damages — subject to whichever cap, if any, genuinely applies to the case, and without ever being told the cap exists.