A good coinsurance percentage is 20% or lower, meaning your insurance covers 80% or more of covered medical costs after you meet your deductible. The most common coinsurance split in employer-sponsored and marketplace plans is 80/20, where the plan pays 80% and you pay 20%. Plans with 10% coinsurance exist but come with higher monthly premiums, so “good” ultimately depends on how you balance monthly costs against the risk of a large medical bill.
How Coinsurance Actually Works
Coinsurance is the percentage of a medical bill you’re responsible for after you’ve already paid your annual deductible. Until that deductible is met, you pay your bills in full at the rate your insurer has negotiated with the provider. Once you cross that threshold, coinsurance kicks in and splits costs between you and your plan.
One detail that trips people up: your coinsurance is calculated on the network-approved amount, not the number on the original bill. Insurance companies negotiate lower rates with in-network providers, and the provider writes off anything above that negotiated price. So if a procedure is billed at $5,000 but the approved amount is $3,500, your 20% coinsurance would be $700, not $1,000.
The formula is simple. Convert your coinsurance percentage to a decimal (20% becomes 0.20), then multiply by the approved cost of the service. That’s your share.
Coinsurance by Plan Tier
If you’re shopping on the ACA marketplace, the metal tier system gives you a clear framework for comparing coinsurance levels. Each tier reflects roughly how much the plan covers versus how much you pay:
- Bronze: The plan pays about 60%, you pay about 40%
- Silver: The plan pays about 70%, you pay about 30%
- Gold: The plan pays about 80%, you pay about 20%
- Platinum: The plan pays about 90%, you pay about 10%
These are averages across all cost-sharing (deductibles, copays, and coinsurance combined), not exact coinsurance rates. But they give you a reliable sense of your financial exposure at each level. A Gold plan with 20% coinsurance is the sweet spot for most people who use healthcare regularly. Bronze plans with 40% coinsurance carry significantly more risk if you need surgery or ongoing treatment, though their premiums are the lowest.
If you qualify for cost-sharing reductions on a Silver plan, your effective share can drop as low as 6%, which is better than Platinum coverage at a Silver-tier premium. These extra savings are only available on Silver plans purchased through the marketplace, and eligibility is based on income.
Why 20% Is the Standard Benchmark
The 80/20 split shows up everywhere in health insurance. Medicare Part B charges 20% coinsurance for covered services after the deductible is met. Most employer-sponsored plans cluster around the same number. It has become the industry default because it keeps premiums manageable while still protecting you from paying the bulk of a major bill.
To put that in real terms: if you have a $10,000 surgery (at the network-approved rate) and you’ve already met your deductible, 20% coinsurance means you owe $2,000. At 30%, that jumps to $3,000. At 40%, it’s $4,000. For a single large medical event, the difference between a “good” and “mediocre” coinsurance rate can easily be a thousand dollars or more.
The Out-of-Pocket Maximum Safety Net
No matter what your coinsurance percentage is, there’s a ceiling on how much you can spend in a year. For 2025, marketplace plans cap out-of-pocket costs at $9,200 for an individual and $18,400 for a family. Once you hit that limit, your plan covers 100% of covered services for the rest of the year.
This matters when you’re weighing plan options. A plan with 40% coinsurance but a $9,200 out-of-pocket max will never cost you more than $9,200 in a catastrophic year, though you’ll reach that ceiling much faster than someone with 20% coinsurance. If you’re generally healthy and mostly want protection against worst-case scenarios, a higher coinsurance plan with a lower premium could make sense. You’re betting that you won’t use much care, and the out-of-pocket max protects you if you’re wrong.
In-Network vs. Out-of-Network Rates
Your coinsurance percentage can change dramatically depending on where you get care. Plans typically charge one rate for in-network providers and a much steeper rate for out-of-network care. A plan that charges you 20% in-network might charge 40% or more out-of-network.
The financial hit goes beyond just the higher percentage. Out-of-network providers aren’t bound by the negotiated rates your insurer has arranged, so the base cost your coinsurance is calculated on may be significantly higher. And out-of-network costs often don’t count toward your regular out-of-pocket maximum, meaning there may be no ceiling on what you owe. When evaluating whether a plan’s coinsurance is “good,” always check both the in-network and out-of-network rates.
Choosing the Right Percentage for You
The best coinsurance percentage depends on how you use healthcare. If you have a chronic condition, take expensive medications, or expect a procedure in the coming year, lower coinsurance (10% to 20%) will almost certainly save you money overall, even with higher premiums. Run the math: multiply your expected medical costs by each coinsurance rate, add the annual premium, and compare totals.
If you rarely see a doctor and mostly want coverage for emergencies, a higher coinsurance plan (30% to 40%) paired with lower premiums might cost less over the course of a year. Just make sure you could handle the out-of-pocket exposure if something unexpected happens. A 40% coinsurance rate on a $50,000 hospitalization adds up fast, even with an out-of-pocket cap limiting your total liability.
For most people landing somewhere in the middle, 20% coinsurance on a Gold-tier or employer plan offers predictable costs without extreme premiums. It’s the most common split for a reason: it keeps your share of any single bill manageable while keeping monthly payments reasonable.