How to Calculate Your Health Plan Coinsurance Payment

Health insurance doesn’t pay all of your health care expenses. Instead, you’re expected to foot the bill for part of the cost of your care through your health plan’s cost-sharing requirements like your deductible, copayments, and coinsurance.

Since deductibles and copayments are fixed amounts, it doesn’t take a lot of math to figure out how much to pay. A $30 copayment to fill a prescription or see a doctor will cost you $30 no matter how much the total bill for the prescription or office visit was. Your health insurance picks up the rest of the tab (note that this generally only applies if you use an in-network provider and fulfill any prior authorization requirements that your insurance plan has).

A nurse talking to her patient in the clinic lobby
Hero Images / Getty Images

However, calculating your health insurance coinsurance payment is trickier. Since coinsurance is a percentage of the total cost for the service, you’ll owe a different amount of coinsurance for each service you receive. If the health care service you received was cheap, your coinsurance won’t be much. However, if the health care service was expensive, your coinsurance could wind up being hundreds or even thousands of dollars (on the high end, your coinsurance will be limited by your health plan's maximum out-of-pocket).

You need to understand how to calculate your health insurance coinsurance payment so you’ll know how much you’ll owe for coinsurance and you can budget for it.

First, Find Your Coinsurance Rate

You’ll need to find your coinsurance rate for the type of care you’re getting. You should be able to locate this in the Summary of Benefits and Coverage you got when you enrolled in your health plan. Sometimes you can even find it on your health insurance card.

Be careful; in some health plans, coinsurance can be the same percentage no matter what type of service you get. For example, 30% coinsurance for hospitalization and 30% coinsurance for specialty drug prescriptions. In other health plans, you might have a low coinsurance rate for some services and a higher rate for other types of service. For example, you could have 35% coinsurance for hospitalization, but only 20% coinsurance for surgery at an outpatient surgery center.

Next, Find the Cost of Your Care

Once you know your coinsurance rate, you need to determine the total cost of the health care service you received. If you’re using an in-network provider, your health plan has already negotiated discounts from that provider. Calculate your health insurance coinsurance payment based on the discounted rate, not the standard rate charged to people who don’t belong to your health plan. Find this in-network discounted amount on your Explanation of Benefits (EOB) listed as “allowed amount" (the EOB will also show the amount the provider billed, which will generally be higher than the allowed amount).

If you haven’t gotten the health care service yet, you won’t have an EOB to check. You can try asking your medical provider or health insurer what the in-network rate for that particular service is. But know that sometimes you simply won't be able to get an accurate estimate of the total cost of your treatment in advance, either because the information is considered proprietary (as part of the network negotiations between the insurer and the medical provider) or because the medical provider won't know in advance exactly what services need to be performed.

If it's a basic service that doesn't vary from case to case (an MRI, for example), the hospital or doctor's office should be able to give you a total price in advance. But if you're having a surgical procedure, the doctor may not know exactly what will be involved until they actually do the surgery. You can rest assured that your health plan's maximum out-of-pocket will kick in if the bill becomes substantial, but if your out-of-pocket maximum isn't met, the amount you'll have to pay in coinsurance could be subject to change.

Last, Calculate Your Coinsurance

To calculate the coinsurance you owe, you’ll first convert your percentage figure into a decimal figure by moving the decimal point two spaces to the left like this:


Corresponding Decimal Figure:

















Now, multiply this decimal figure by the total cost of the health care service:
Coinsurance rate (as a decimal figure) X total cost = coinsurance you owe.


Antoine’s health plan requires 20% cost-sharing to fill a prescription. His total prescription cost is $150.
0.20   X   $150.00   =   $30.00
Coinsurance rate X total cost = coinsurance Antoine owes.
Antoine owes $30 coinsurance for this particular prescription.

Kinsey’s health plan requires 35% cost-sharing for hospitalizations. The total cost for her hospital stay, after she pays her deductible, is $12,850.00
0.35   X   $12,850   =   $4,497.50
Coinsurance rate X total cost = coinsurance Kinsey owes.
Kinsey will owe $4,497.50 in coinsurance charges for her hospitalization, in addition to the amount of her deductible (that's assuming she hasn't yet met her health plan's out-of-pocket maximum yet).

Factors Affecting Your Coinsurance Amount

Don’t forget that you must also pay your deductible. On some health plans, you’ll have to pay the entire deductible before your health plan begins to pay part of the cost of your non-preventive care. Only after you’ve paid your full deductible will you be sharing the cost of your care with your health plan by paying coinsurance.

If you have a really big health care bill, your out-of-pocket maximum might kick in and protect you from some of the cost. Once the deductibles, copayments, and coinsurance you’ve paid this year add up to the out-of-pocket maximum, your cost-sharing requirements are finished for the year. Your health plan picks up 100% of the cost of your covered in-network care for the rest of the year. You don’t have to pay coinsurance, copays, or deductibles again until next year...usually.

In 2020, all non-grandfathered, non-grandmothered plans must have out-of-pocket maximums that don't exceed $$8,150 for a single individual and $16,300 for a family (those upper limits will increase to $8,550 and $17,100 in 2021). But many plans have out-of-pocket maximums that are well below these limits.

Thanks to the Affordable Care Act, most preventive care must be covered by your health insurance without requiring coinsurance, copayments, or even a deductible. This means you won’t have to pay coinsurance on things like your yearly physical exam, yearly mammogram, and routine immunizations. Although it may seem like preventive care is free, it’s not. Instead, the cost of that preventive care is included in your monthly health insurance premium whether or not you actually use the care.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Federal Register. Department of Health and Human Services. Patient Protection and Affordable Care Act; HHS Notice of Benefit and Payment Parameters for 2020. April 25, 2019.

  2. U.S. Department of Health and Human Services. Patient Protection and Affordable Care Act; HHS Notice of Benefit and Payment Parameters for 2021; Notice Requirement for Non-Federal Governmental Plan. May 14, 2020.