How Does Health Insurance Work? A Plain-English Guide

How does health insurance work?

Health insurance is a cost-sharing arrangement. You pay a predictable amount each month, and your plan covers a share of medical costs.

That's the tradeoff. Your premium is certain and predictable, while a surgery or an emergency room visit is not. Insurance turns a bill you can't plan for into one you can.

Part one: your premium

Your premiumFixed amount, taken from each paycheck. You pay these no matter how much care you use. is the price of having coverage. You pay it whether or not you see a doctor that year.

On an employer plan, the premium is split between you and your employer, and your share comes out of your paycheck.^[1] Your premium does not count toward your deductible or your out-of-pocket max.

For a closer look at how the premium trades off against the deductible, see Premium vs Deductible.

Part two: your deductible

Your deductibleThe amount of medical bills you need to pay in a year before insurance starts splitting the bills with you. is the amount you pay for covered care before your plan starts paying its share. If your deductible is $2,000, you cover the first $2,000 of bills yourself.

Two things soften that. Most plans cover preventive careMost plans cover preventive care at no extra cost when you use in-network providers. at no cost before you meet the deductible, as long as you see an in-network provider.^[2] And many plans charge fixed copays for routine visits that apply right away, deductible or not.

Your deductible resets at the start of each plan year. What you spent last year doesn't carry over.

Part three: copays and coinsurance

Once you've met your deductible, you and your plan split the cost of care. That split takes one of two forms.

A copayA fixed dollar amount you pay for certain services (like office visits or prescriptions). Copay plans often have higher premiums but lower costs for routine care. Copays usually do not count toward your deductible, but they typically count toward your out-of-pocket maximum. is a fixed dollar amount for a service, like $30 for a doctor visit. You know the cost before you walk in.

CoinsuranceAfter you reach your deductible, this is the percent of each bill you pay while insurance pays the remainder. is a percentage of the bill. At 20% coinsurance, a $4,000 procedure costs you $800 and your plan covers the other $3,200. The bigger the bill, the bigger your share.

Most plans use both: copays for routine visits, coinsurance for larger costs. For the full breakdown, see Copay vs Coinsurance.

Part four: your out-of-pocket max

Your out-of-pocket maxThe most you pay for covered medical bills in a year. After this, insurance pays 100% of covered costs. is the most you'll pay for covered in-network care in a plan year. Once your spending hits that limit, your plan covers 100% for the rest of the year.^[3]

Your deductible, copays, and coinsurance all count toward it. Your premium doesn't.^[4] Think of it as a spend ceiling.

For more on how the deductible and out-of-pocket max relate, see Deductible vs Out-of-Pocket Max.

Why your network matters

Those four numbers usually apply only to in-networkIn-network providers have negotiated rates. Out-of-network services are usually much more expensive. care, meaning providers your plan has a contract with. Go out of network and you often face a separate, higher deductible, a higher out-of-pocket max, or no coverage at all.^[5]

How strict that network is depends on the plan type. See HMO vs PPO vs EPO and In-Network vs Out-of-Network for how network rules change what you pay.

So which plan costs the least?

The plan with the lowest premium isn't automatically the cheapest. A lower premium almost always means a higher deductible.

Your real cost for the year is the premium plus whatever you pay in cost-sharing for the care you actually use. A healthy year and a year with surgery can flip which plan wins.

That's the comparison our calculator is built for.

Compare plans on total annual cost

Use our calculator to enter the premium, deductible, coinsurance, and out-of-pocket max for each plan and compare your total annual cost across low, medium, and high care scenarios.

Sources

1. KFF 2025 Employer Health Benefits Survey — employer and employee premium cost-sharing on employer-sponsored plans [1]
2. HealthCare.gov — Preventive Care Benefits — ACA requirement for no-cost preventive care before the deductible for in-network providers [2]
3. HealthCare.gov — Out-of-Pocket Maximum/Limit — plan pays 100% of covered in-network care after the out-of-pocket max is reached [3]
4. HealthCare.gov — Your Total Costs for Health Care — premiums do not count toward the deductible or out-of-pocket max [4]
5. HealthCare.gov — Health Insurance Plan & Network Types — out-of-network coverage rules by plan type (HMO, PPO, EPO) [5]