Compare HSA and FSA based on your health spending and retirement goals.
HSA total value
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Tax savings + retirement growth.
FSA modeled value
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Tax savings plus any permitted one-year carryover.
Difference
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Your breakdown
Updates live as you type| Component | HSA | FSA |
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One account you keep, one you forfeit
Health savings accounts and flexible spending accounts both let eligible medical spending receive favorable federal tax treatment, and that surface similarity hides a deep difference. An FSA is generally use-it-or-lose-it: money you do not spend by the plan deadline is forfeited, though an employer may allow a carryover of up to $680 for 2026 or offer a grace period instead. An HSA belongs to the account holder. Unspent balances carry forward, may be investable, and can be withdrawn federally tax-free for qualified medical expenses. The catch is eligibility. You can contribute to an HSA only with qualifying coverage and without disqualifying coverage, while a health FSA must be offered by an employer. This tool compares the selected contribution under simplified assumptions; it does not compare the underlying health plans.
Where the triple tax advantage comes from
Under federal rules, an eligible HSA contribution may be deductible or excluded from wages, earnings are not taxed while inside the account, and qualified medical withdrawals are tax-free. A health FSA also lets eligible expenses be paid with pre-tax salary reductions, but its balance generally cannot become a long-term investment account. State and payroll-tax treatment can differ. This calculator uses only the income-tax rate you enter and does not model FICA.
$3,000 a year, twenty-five years later
Consider someone contributing $3,000, expecting $1,500 of medical spending this year, in a 32% marginal bracket, with 25 years until retirement and a 7% investment return on the invested HSA balance. Both accounts deliver the same immediate tax saving of $960. The difference is what happens to the rest.
The HSA's modeled value is about $9,101. If the FSA plan permits the 2026 maximum carryover, $680 of the $1,500 unused balance carries into the next plan year and $820 is forfeited, producing a modeled FSA value of $1,640 when that carryover is added to the $960 tax saving. The displayed gap is therefore about $7,461. The HSA figure assumes the unspent amount remains invested for all 25 years; the FSA carryover remains available only under the employer plan's terms and is not a retirement investment.
When leaving HSA money invested may help
The HSA projection becomes larger only because the example leaves part of the contribution invested. Paying current medical bills from other cash can preserve HSA assets, but it also uses household liquidity and exposes the retained balance to investment losses. Keep records for any delayed reimbursement and use this approach only if current bills and emergency reserves remain covered. The calculator is a scenario comparison, not a recommendation to defer every HSA withdrawal.
What actually counts as a qualified medical expense?
Broader than most people assume. The IRS defines qualified medical expenses in Publication 502, and it covers far more than copays and prescriptions: dental work, vision care and glasses, mental health treatment, physical therapy, and many medical devices all qualify. Since 2020, over-the-counter medicines and menstrual products count too, without a prescription. What generally does not qualify is cosmetic surgery, gym memberships, and everyday toiletries. Insurance premiums are usually not qualified for HSA purposes while you are working, with narrow exceptions such as COBRA, long-term care premiums, and, once you are on Medicare, your Medicare premiums. When in doubt, check Pub 502 before you reimburse yourself, because a non-qualified withdrawal before age 65 is taxed and hit with a 20% penalty.
What happens to my HSA after age 65?
It gets even better. After 65 you can withdraw HSA funds for any reason and pay only ordinary income tax, with no penalty, which makes the account behave like a traditional IRA for non-medical spending. Qualified medical withdrawals remain completely tax-free at any age, and you can use the HSA tax-free for Medicare premiums. By contrast, an FSA has no role in retirement at all. This flexibility is the reason the HSA is often called the most tax-advantaged account available to ordinary savers.
Does a high-deductible plan make the HSA not worth it?
It depends on your health spending, and you should compare total cost, not just premiums. A high-deductible plan trades a lower monthly premium for a higher deductible, so a year with a major medical event can cost you more out of pocket than a richer plan would. But the lower premiums often free up cash that you can route into the HSA, and the tax savings plus growth can more than make up the difference for healthy people. Run both the premium difference and a bad-year scenario before deciding; the HSA is a strong asset, but only if the underlying plan fits how much care you actually use.