HSA vs FSA Calculator
Compare an HSA and an FSA. Both cut this year taxes, but only an HSA rolls over and grows tax-free.
Want to understand the concept, not just the number? Read The Insurance Decisions Guide .
How it's calculated
Health savings accounts and flexible spending accounts both let you set aside pre-tax money for medical costs, so both cut this year tax bill by your marginal rate. The difference shows up over time. An FSA is use-it-or-lose-it, so whatever you do not spend by year end is gone. An HSA rolls over every year, can be invested, and grows completely tax-free, which makes it one of the most powerful accounts in the tax code.
Take the default. You put $4,000 a year into the account and you are in the 22 percent bracket, so each year you save $880 in taxes either way. But with an HSA, if you can pay your medical bills out of pocket and leave the account invested at 7 percent for 20 years, your contributions grow to about $173,642. Since you put in $80,000, that is roughly $93,642 of tax-free growth, money an FSA can never build because it forces you to spend each year contribution.
The catch is that an HSA requires a high-deductible health plan, and its power only shows if you let the balance grow rather than spending it right away. An FSA still makes sense if you do not have a high-deductible plan or you have known, recurring medical costs to cover this year. But if you can use an HSA and invest it, the long-term growth advantage is large, and after age 65 you can withdraw for any reason paying only ordinary tax, like a traditional retirement account.
Assumptions
- Both accounts give the same upfront income-tax saving at your marginal rate. The difference is that an HSA rolls over and can be invested, while an FSA must be spent each year.
- The growth advantage assumes you pay medical costs out of pocket and leave the HSA invested. It uses your marginal rate from the 2026 brackets and monthly compounding. An HSA requires a high-deductible health plan.
Last updated: 2026-08-08 · Tax year 2026
These assumptions follow our general methodology.
Frequently asked questions
What is the difference between an HSA and an FSA?
Both are pre-tax accounts for medical costs, but an HSA rolls over year to year, can be invested, and grows tax-free, while an FSA is largely use-it-or-lose-it within the year. An HSA requires a high-deductible health plan; an FSA does not. The HSA is far better for long-term saving.
Is an HSA better than an FSA?
For long-term saving, yes, because the money rolls over and grows tax-free, and after 65 you can use it for anything. An FSA can still be the right choice if you do not have a high-deductible health plan or you have predictable medical spending to cover this year with the tax break.
Why is an HSA called triple tax-advantaged?
Contributions go in pre-tax, the money grows tax-free while invested, and withdrawals for qualified medical expenses are tax-free too. No other account offers all three. This calculator focuses on the growth leg, which is the one an FSA cannot match.
Can I lose the money in an FSA?
Yes. FSAs are generally use-it-or-lose-it, though some plans allow a small carryover or a short grace period. Money left unspent at the deadline is forfeited, which is why FSAs suit known, near-term costs rather than long-term saving.