Calculate Your Medical Costs The amount a patient owes = The Copay + Coinsurance + Any Remaining Deductible. Follow these steps to calculate your actual medical costs; Step 1: Get a Service Description and CPT Code® from your physician’s practice Step 2: Contact Insurance Provider and use the information in Step 1 to get the insurance company’s contracted rate for the service noted in “Step 1.” Step 3: While speaking with the customer service for your insurance company, learn your co-payment amount, your coinsurance percent, and your remaining deductible amount. Step 4: Multiply your coinsurance percent by the insurance company’s contracted rate for that specific service. Step 5: Add your coinsurance amount to your co-payment amount. Step 6: Add any remaining deductible amount to your co-payment + coinsurance amount.