HSA vs FSA Calculator
What you will contribute, what you expect to spend, and your rates
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Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Educational estimate only. Confirm the assumptions, current rules, fees, and rounding that apply to your situation before making a decision.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter what you would contribute for the year. Use the same figure for both accounts — the page prices one contribution two ways, so the comparison is like for like.
- 02
Enter the qualified medical spending you genuinely expect, not the spending you hope to have. This single number decides how much an FSA forfeits, and it is the input people get wrong.
- 03
Fill in your marginal federal rate, your state rate, and leave the FICA rate at 7.65% unless you know yours differs. The three together are what either account saves you through payroll.
- 04
Set the years you would leave unspent HSA money invested and the return you expect. An HSA's advantage is compounding, and at zero years it has almost none.
- 05
Check your employer's FSA carryover in the advanced panel — the 2026 maximum is $680, and some plans offer a 2½-month grace period instead, in which case enter 0. Then read the schedule, which reruns both accounts across six levels of spending.
Formula
Both accounts save the same tax through payroll: Tax saved = contribution × (federal rate + state rate + FICA rate) An HSA funded outside payroll and deducted on Form 8889 saves only (federal + state). The FSA's risk is forfeiture: Unspent = contribution − expected spending Forfeited = the part of Unspent above the carryover FSA benefit = Tax saved − Forfeited The HSA's advantage is that nothing is forfeited and what stays invested compounds: HSA benefit = Tax saved + (Unspent × (1 + return)^years − Unspent) The gap between them is therefore the forfeiture plus the growth: HSA ahead by = Forfeited + growth on Unspent Forfeiture starts as soon as spending falls below (contribution − carryover). Because growth and forfeiture are both never negative, the HSA weakly wins at every level of spending whenever both accounts are available — which is why the page frames the choice as an eligibility question rather than a maths question.
Example
Contribute $3,000, expect $2,400 of qualified spending, pay 22% federal, 5% state and 7.65% FICA, and leave unspent money invested for 20 years at 6%. The combined rate is 34.65%, so $3,000 saves $1,040 of tax in either account — or $810 if you fund the HSA yourself rather than through payroll, because the $230 of FICA is only avoided by a payroll deduction. Spending $2,400 forfeits nothing in the FSA, because forfeiture only starts below $2,320 once the $680 carryover is counted, so the FSA benefit is the full $1,040. The HSA keeps the $600 you did not spend, which grows to $1,924 over the 20 years, $1,324 of it untaxed gains. That leaves the HSA $1,324 ahead. Pay the $2,400 of bills from cash instead and the whole $3,000 compounds to $9,621. The page's schedule shows how fast the gap widens when spending disappoints: at $1,500 of spending the FSA forfeits $820 and nets $220 while the HSA nets $4,350, and at no spending at all the FSA loses $1,281 on the year while the HSA nets $7,661. Rerunning the whole page at $1,200 of expected spending forfeits $1,120, turning the FSA into a net loss of $81 while the HSA nets $5,012.
Definitions
- Health savings account (HSA)
- A personal account for medical costs, open only to people covered by a qualifying high-deductible plan. Contributions are deductible or pre-tax, growth is untaxed, withdrawals for qualified medical expenses are untaxed, and the balance rolls over for life.
- Health flexible spending arrangement (FSA)
- An employer cafeteria-plan account funded by salary reductions before tax. The whole election is available from the first day of the plan year, but money left at the end is forfeited apart from a carryover or grace period.
- Carryover
- The unused health FSA money a plan may let you keep for the following plan year — up to $680 for 2026 (Rev. Proc. 2025-32 §3.17). A plan may offer a carryover or a grace period, but not both.
- Grace period
- Up to 2½ months after the plan year in which leftover FSA money can still pay expenses. Coverage by a general purpose FSA during a grace period blocks HSA contributions unless the FSA balance was zero at the year end.
- Limited-purpose FSA
- An FSA restricted to dental, vision and preventive care. Because it does not reimburse general medical expenses, it can sit alongside an HSA without ending eligibility.
Good to know
Two accounts that look alike and behave nothing alike
A health savings account and a health flexible spending arrangement are both ways of paying medical costs with money that never gets taxed, which is why people treat them as interchangeable. They are not. An FSA is an employer arrangement: you elect an amount before the plan year starts, it comes out of your pay in equal slices, and at the end of the year whatever you have not spent is forfeited, apart from a carryover of up to $680 for 2026 or a grace period of up to two and a half months. An HSA is your own account, attached to you rather than to a job. Nothing in it is ever forfeited, it moves with you when you change employer, and it can be invested. The tax treatment in the year of contribution is identical when both run through payroll. At the page's example of a $3,000 contribution with a 22% federal rate, 5% state rate and 7.65% FICA, the combined 34.65% saves $1,040 either way. Everything that separates them happens afterwards. The FSA's $1,040 is the end of the story; the HSA keeps whatever you did not spend and lets it compound. With $2,400 of expected spending, the $600 left over grows to $1,924 over twenty years at 6%, putting the HSA $1,324 ahead. Run the same page at $1,200 of spending and the difference becomes stark: the FSA forfeits $1,120 and ends the year $81 down, while the HSA nets $5,012. The arithmetic only ever points one way when both accounts are open to you, which is why this page frames the decision as a question about eligibility rather than a question about maths.
Why you usually cannot have both, and the exception that matters
The reason most people never have to choose carefully is that the choice is made for them by their health plan. An HSA requires a qualifying high-deductible plan: for 2026 that means a deductible of at least $1,700 for self-only coverage or $3,400 for family coverage, with out-of-pocket costs capped at $8,500 and $17,000 (Rev. Proc. 2025-19 §2.01). If your employer offers no such plan, the FSA is your only pre-tax route and the comparison is academic. Where both are available, they generally cannot be held together. Publication 969 states that an employee covered by a high-deductible plan and a health FSA that reimburses qualified medical expenses generally cannot contribute to an HSA, because the FSA counts as other coverage that pays before the deductible is met. The exception is worth knowing because it is genuinely useful: a limited-purpose FSA, which reimburses only dental, vision and preventive care, can sit alongside an HSA without ending eligibility. So can a post-deductible FSA, which pays nothing until the minimum deductible has been met. Many employers offering a high-deductible plan also offer a limited-purpose FSA precisely so employees can use both. There is one trap at the boundary of a plan year. Coverage during an FSA grace period by a general purpose FSA blocks HSA contributions unless the balance in that FSA was zero when the prior plan year ended. Someone who switches to a high-deductible plan in January while carrying leftover general-purpose FSA money into a grace period can therefore be disqualified for the first months of the new year without realising it. Spending the FSA down to zero before the year ends avoids the problem entirely.
Forfeiture, and the one thing an FSA does better
Forfeiture is the FSA's defining risk and the reason the expected-spending field matters more than any other on the page. At a $3,000 election with the $680 carryover, forfeiture begins the moment spending falls below $2,320. Above that level nothing is lost; below it, every dollar of shortfall beyond the carryover disappears at the end of the plan year. The page's schedule makes the slope visible: at $1,500 of spending the FSA forfeits $820 and the year's benefit falls to $220, and with no spending at all it forfeits $2,320 and the year is a net loss of $1,281 despite the tax saving. This is why the standard advice is to elect only what you are confident you will spend. Predictable costs — a known prescription, orthodontics already scheduled, regular therapy — are what an FSA is for. Speculative ones are not. Note also that a plan may offer a carryover or a grace period but not both, so check which one yours has; if it runs a grace period rather than a carryover, enter 0 in the carryover field and the forfeiture threshold rises to the full election. Against all this, an FSA does one thing an HSA cannot, and in the right circumstances it is decisive. Publication 969 requires the plan to make the maximum amount of reimbursement — the full amount you elected for the year — available at any time during the coverage period, regardless of how little has actually been deducted from your pay. Elect $3,000 in January and the whole $3,000 is there in January, even though you have contributed almost nothing. An HSA only ever holds what has been paid into it. For someone facing a large known expense early in the year with no savings to bridge it, that timing advantage is real money, and it is the one honest argument for choosing the FSA when both are available.
The FICA detail, and what the HSA is really for
One difference is easy to miss and worth a few hundred dollars a year. Both an FSA salary reduction and an HSA contribution made through an employer's cafeteria plan come out of pay before federal income tax, state income tax and Social Security and Medicare tax. Fund an HSA yourself instead — moving money from a bank account and deducting it on Form 8889 — and you save the income tax but not the 7.65% FICA. On the example that is the difference between $1,040 and $810, or $230 a year, for exactly the same contribution. Anyone whose employer offers HSA contributions through payroll should use that route rather than making the deposit personally and claiming it back at tax time. People who are self-employed have no payroll to run it through, so the $810 figure is the one that applies to them. The larger point is what an HSA is for once you stop thinking of it as a way to pay this year's bills. Contributions are untaxed, growth is untaxed, and withdrawals for qualified medical expenses are untaxed, which no other account offers. Money left invested for decades compounds without ever being taxed: at the example's 6% over twenty years, paying the $2,400 of bills from cash instead of from the account leaves the whole $3,000 to grow to $9,621. Used that way an HSA behaves like a retirement account reserved for the costs that reliably arrive in later life. That strategy needs cash available to pay current bills, so it is not open to everyone, and it is worth remembering that once Medicare starts, contributions stop entirely — though the balance already built stays available for the rest of your life. The 2026 limits are $4,400 for self-only coverage and $8,750 for family, plus $1,000 more from age 55.
Frequently asked questions
Is an HSA better than an FSA?
On the money, yes, whenever both are open to you. At the page's example — $3,000 contributed, $2,400 of expected spending, a 34.65% combined rate and 20 years at 6% — both accounts save the same $1,040 of tax, but the $600 you do not spend stays in the HSA and grows to $1,924, so the HSA ends up $1,324 ahead. The FSA can only ever match the tax saving; it cannot beat it. The real question is not which account is better but whether you can hold the high-deductible plan an HSA requires.
Can I have both an HSA and an FSA?
Not a general purpose health FSA. Publication 969 says an employee covered by a high-deductible plan and a health FSA that reimburses qualified medical expenses generally cannot contribute to an HSA, because the FSA counts as other coverage. A limited-purpose FSA can sit beside an HSA, because it pays only dental, vision and preventive care. A post-deductible FSA also works. One trap catches people at year end: coverage during an FSA grace period by a general purpose FSA is only allowed if the balance in that FSA was zero when the plan year ended.
How much do I forfeit if I do not spend my FSA?
Everything above the carryover. At the example's $3,000 contribution with the $680 carryover, forfeiture begins the moment spending falls below $2,320. Spending $2,400 forfeits nothing. Rerunning the page with spending of $1,200 forfeits $1,120, which turns a $1,040 tax saving into a net loss of $81 for the year. A plan may offer a carryover or a grace period of up to 2½ months, but Publication 969 does not let it offer both.
Does an HSA save FICA tax too?
Only if it is funded through payroll. An FSA salary reduction and an HSA contribution made through an employer's cafeteria plan both come out of pay before federal income tax, state income tax and Social Security and Medicare tax. Fund the HSA yourself from a bank account and deduct it on Form 8889 and you save the income tax but not the 7.65% FICA. In the example that difference is $230 a year: $1,040 saved through payroll against $810 saved on your own.
How much can I put in each account in 2026?
A health FSA takes up to $3,400 in salary reductions, with up to $680 carried into the following year if the plan allows it (Rev. Proc. 2025-32 §3.17). An HSA takes $4,400 on self-only coverage or $8,750 on family coverage, plus $1,000 more from age 55 (Rev. Proc. 2025-19 §2.01). The example's $3,000 fits either account.
What does an FSA do better than an HSA?
It gives you the whole election on day one. Publication 969 requires the plan to let you receive the maximum amount of reimbursement — the amount you elected for the year — at any time during the coverage period, however little has actually been deducted from your pay. Elect $3,000 in January and the full $3,000 is available in January. An HSA only ever holds what has been paid in. For a known expense early in the year, that timing is worth real money.
What if I cannot get a high-deductible plan?
Then the comparison does not arise and the FSA is your pre-tax option. An HSA requires a qualifying plan: for 2026 a deductible of at least $1,700 for self-only or $3,400 for family cover, with out-of-pocket costs no higher than $8,500 and $17,000 (Rev. Proc. 2025-19). If your employer offers no such plan, contribute to the FSA only what you are confident you will spend, since the forfeiture risk is the whole downside.