Is there a “formula” for determining compensation/settlement in a personal injury case?

There isn't any mathematical formula for determining pain and suffering.  When you complete your medical treatment and are released by the doctor or are declared by the doctor to be permanent and stationary which means having reached a point in your treatment where no further improvement is anticipated, obtain your medical bills, medical reports and documentation of wage loss.  Compensation for the medical bills is straight reimbursement.  The medical reports will document the nature and extent of your injury and will be used to determine compensation for pain and suffering, which is an amount in addition to the medical bills. (Compensation for emotional distress would also depend on the medical bills and medical reports). Compensation for wage loss is straight reimbursement.  Wage loss is NOT a factor in determining compensation for pain and suffering.

If you have residual complaints of pain after completing your medical treatment and those residual complaints are documented in the medical report, your compensation for pain and suffering would be more than someone who had fully recovered and did not have residual complaints of pain.  If the medical reports state that you will need future treatment with an estimated cost discounted to present value, your pain and suffering compensation will be more than someone who does not need additional treatment.  If you have scars or burns, your compensation for pain and suffering will be more than someone who does not have scars or burns.  Therefore, determining compensation for pain and suffering depends on the facts documented in the medical reports.

If you have fully recovered, I would ask for quadruple the medical bills to compensate for pain and suffering, but NOT expecting to get that.  The insurance carrier will respond with a much lower offer, and you can continue negotiating with the insurance carrier to try to get it to increase its offer.  If the case is settled, NO lawsuit is filed.  If you are dissatisfied with settlement offers from the property owner's insurance carrier, reject the settlement offers and file a lawsuit based on premises liability.  If the case is NOT settled with the insurance carrier, your lawsuit must be filed prior to the expiration of the applicable statute of limitations or you will lose your rights forever in the matter.