Health
What Is Coinsurance?
Coinsurance is your share of covered costs after the deductible, expressed as a percentage. See how 20% coinsurance works with a simple example.
By InsureGuide Editorial Team. Published May 21, 2026. Updated August 8, 2026.
Coinsurance is a percentage split of a covered bill after you have met the deductible (unless the plan says otherwise). If coinsurance is 20%, the plan’s share is often 80% of the allowed amount for that service, until you reach the out-of-pocket maximum.
A simple illustration
Suppose the deductible is already met, the allowed amount for a procedure is $2,000, and coinsurance is 20%. Your coinsurance would be $400, and the plan would be responsible for $1,600 of that allowed amount, ignoring other adjustments.
If the deductible is not yet met, you may pay the remaining deductible first. Our health cost calculator uses this kind of simplified sequence for education only.
Coinsurance vs copay
A copay is usually a flat dollar amount, such as $30 for a primary-care visit. Coinsurance is a percentage of the allowed charge. Some plans use copays for office visits and coinsurance for hospital care.
Allowed amounts matter
The percentage applies to the plan’s allowed amount, not necessarily the provider’s full billed charge. Out-of-network balance billing can still occur where not prohibited by law. Surprise-billing protections under federal law apply to many emergency and certain in-network situations; details are beyond this overview.