Coinsurance is a type of cost-sharing arrangement in which the patient is responsible for a percentage of the total cost of medical services, while the insurance company pays the remainder. It is typically expressed as a percentage, such as 20% or 30%.

To calculate coinsurance on a medical bill, you first need to determine the total cost of the services provided. This may include charges for office visits, diagnostic tests, treatments, and medications.

Next, you need to check your insurance policy to determine the percentage of coinsurance that you are responsible for. For example, if your policy has a 20% coinsurance rate, you will be responsible for paying 20% of the total cost of the services provided.

To calculate your coinsurance payment, you simply multiply the total cost of the services by your coinsurance percentage. For example, if the total cost of the services provided was $1,000 and your coinsurance rate is 20%, your coinsurance payment would be $200 (i.e., 20% of $1,000).

It's important to note that coinsurance is typically applied after your deductible has been met. So if you have a $1,000 deductible and the total cost of services is $5,000, you would be responsible for paying your deductible first ($1,000) and then your coinsurance payment based on the remaining $4,000.