HSA vs FSA Calculator
Compare payroll tax savings, forfeiture risk, and long-term rollover growth between an HSA and a Health FSA.
HSA vs FSA Comparison
HSA Tax Savings
$1,040
FSA Tax Savings
$1,040
Tax savings are nearly identical dollar-for-dollar — the real difference is what happens to money you don't spend.
With an FSA, you'd forfeit $820 this year (unspent balance beyond the $680 carryover allowance, if your plan offers one).
What Is the HSA vs FSA Calculator?
A Health Savings Account (HSA) and a Health Flexible Spending Account (FSA) both let you set aside pre-tax money for medical expenses through payroll deduction, and both reduce your federal tax, state tax, and FICA (Social Security/Medicare) wages by the same mechanism — so for an equal contribution amount, the immediate payroll tax savings are essentially identical. The real difference between them isn't the tax treatment going in, it's what happens to money you contribute but don't spend by year-end, and this calculator is built specifically to make that difference visible in dollars rather than just as a rule you have to take on faith.
An HSA requires enrollment in a qualifying High-Deductible Health Plan (HDHP), but in exchange, unspent HSA funds roll over indefinitely, can be invested, and grow completely tax-free — there's no "use it or lose it" deadline, ever, and the account is yours even if you change employers. An FSA doesn't require an HDHP, but unspent funds beyond a small IRS-set carryover limit are forfeited back to your employer at the end of the plan year (or grace period, if your employer offers one instead of a carryover — plans can offer one or the other, not both).
For the broader picture of how pre-tax benefits affect your paycheck, see the Take-Home Pay After Benefits Calculator, which treats HSA/FSA contributions the same way this one does for payroll tax purposes.
HSA vs FSA Calculator Formula
Tax Savings = Contribution × (Federal Rate + State Rate + FICA Rate)
FSA Forfeited = max(0, (Contribution − Expenses) − Carryover Limit)
HSA Rollover Future Value = Unspent Balance × [((1 + r)^n − 1) / r]
How Is the HSA vs FSA Calculator Calculated?
Both accounts' tax savings use the same formula because both are funded through a Section 125 cafeteria plan, which excludes the contribution from federal income tax, most state income tax, and FICA wages alike — the only reason the two tax-savings figures differ in the results above is that each account has a different contribution limit, which can cap how much actually goes in.
The FSA forfeiture calculation assumes your employer offers the maximum IRS-allowed carryover ($680 for 2026) — some employers offer a smaller carryover, a grace period instead, or neither, so check your specific plan's rules rather than assuming the maximum applies. The HSA side has no forfeiture calculation at all, because unspent HSA funds are never lost — the future-value figure simply shows what that balance could be worth if left invested rather than spent.
HSA vs FSA Calculator Example
Self-only coverage, contributing $3,000 with $1,500 in expected expenses, at a combined 22% federal + 5% state + 7.65% FICA rate: both accounts save about $1,040 in tax. But the $1,500 left unspent means an FSA would forfeit $820 (after the $680 carryover), while the same $1,500 in an HSA is never lost — invested for 10 years at 6%, it could grow to roughly $19,771.
Family coverage, maxing an HSA at $8,750 with $4,000 in expenses, at 24% federal and no state tax: the HSA saves about $2,769 in tax — meaningfully more than an FSA's $1,076, purely because the FSA's $3,400 limit caps how much can go in tax-advantaged in the first place, regardless of forfeiture.
How to Use the HSA vs FSA Calculator
Step 1
Select your HDHP coverage type (self-only or family) to set the HSA limit.
Step 2
Confirm whether you're actually HSA-eligible (enrolled in a qualifying HDHP).
Step 3
Check the age 55+ box if you qualify for the HSA catch-up contribution.
Step 4
Enter the amount you plan to contribute and your expected annual medical expenses.
Step 5
Enter your federal and state marginal tax rates.
Step 6
Set a projection period to see the long-term value of HSA rollover growth.
Benefits
- Shows that HSA and FSA tax savings are nearly identical for the same contribution, correcting a common assumption that one has a bigger tax advantage than the other.
- Quantifies FSA forfeiture risk in real dollars based on your own expense estimate.
- Projects the long-term value of HSA funds you don't spend, since they roll over and can be invested.
- Applies current 2026 IRS contribution limits and the FSA carryover rule automatically.
- Free, instant, and runs entirely in your browser.
Common HSA vs FSA Calculator Scenarios
Scenario 1
Deciding between HSA and FSA during open enrollment when your employer offers a choice.
Scenario 2
Estimating how much you might forfeit in an FSA if your medical expenses come in lower than expected.
Scenario 3
Understanding the long-term opportunity cost of choosing FSA over HSA if you're HSA-eligible.
Scenario 4
Comparing employer plans that offer different HDHP and FSA combinations.
Scenario 5
Explaining to a new hire why "max your HSA" is common financial advice when available.
Understanding Your Result
The tax savings figures show what you keep in your pocket this year purely from the pre-tax contribution mechanism — they're similar between the two accounts because the mechanism is the same. The forfeiture and rollover figures show the part that actually differentiates the two: money you don't end up spending is gone under an FSA (beyond the carryover) but preserved and potentially growing under an HSA.
If you're not HSA-eligible because you're not enrolled in a qualifying HDHP, none of the HSA figures apply to you this year — an FSA (or no pre-tax medical account at all) are your only options until you have HDHP coverage.
Tips
- If you're HSA-eligible and can afford to pay some medical costs out of pocket, contributing to your HSA and letting the balance ride (paying expenses from cash instead) maximizes long-term tax-free growth.
- Estimate FSA contributions conservatively — it's generally safer to slightly underfund an FSA than to lose money to forfeiture.
- HSA funds can be used for non-medical expenses after age 65 without penalty (just ordinary income tax, like a traditional IRA) — before 65, non-medical withdrawals incur both tax and a 20% penalty.
- Some employers offer an FSA grace period (extra time to spend prior-year funds) instead of a carryover — check which one your plan offers, since they're not the same and not usually both available.
- An HSA is portable between jobs; an FSA generally is not (beyond limited COBRA continuation) — factor that into the comparison if you expect to change employers.
Common Mistakes
- Assuming an FSA has a bigger tax advantage than an HSA, or vice versa, when the payroll tax mechanism is actually the same for both.
- Over-contributing to an FSA based on an optimistic expense estimate and then forfeiting the unspent balance.
- Forgetting that an HSA requires HDHP enrollment — you can't simply choose an HSA over an FSA if your health plan isn't a qualifying HDHP.
- Not realizing FSA carryover and grace-period rules are employer-plan-specific, and assuming the maximum IRS-allowed carryover automatically applies.
- Ignoring the investment/rollover angle entirely and evaluating HSA vs FSA purely as "which one saves more tax this year."
Frequently Asked Questions
Can I have both an HSA and a Health FSA at the same time?
Generally no for a standard Health FSA, since having other pre-tax health coverage (aside from the HDHP itself) can disqualify you from HSA eligibility — a 'limited-purpose FSA' (covering only dental and vision) is a common workaround some employers offer alongside an HSA.
What happens to unused FSA money at the end of the year?
It's forfeited back to your employer, except for whatever your plan allows you to carry over (up to $680 for 2026) or spend during a grace period, if your employer offers either option.
What happens to unused HSA money at the end of the year?
Nothing — it simply stays in your account and rolls over indefinitely, with no deadline to spend it, unlike an FSA.
Do I lose my HSA if I change jobs?
No — an HSA is owned by you personally, not your employer, so it stays with you regardless of job changes. An FSA is employer-owned and is generally forfeited when you leave, subject to limited COBRA continuation rules.
Can I invest my HSA balance?
Most HSA providers let you invest balances above a certain threshold (often a few thousand dollars) in mutual funds or similar options, similar to a 401(k) — this is what allows the tax-free growth this calculator projects. FSA balances cannot be invested.
Why are the tax savings for HSA and FSA almost the same in this calculator?
Both are funded through a Section 125 cafeteria plan, which excludes contributions from federal tax, most state tax, and FICA wages using the same mechanism — the only difference in the tax-savings figure comes from each account's different contribution limit potentially capping the amount.
Is the FSA carryover amount guaranteed?
No — $680 (2026) is the maximum the IRS allows employers to offer, but employers can offer a smaller carryover, a grace period instead, or nothing at all. Check your specific plan documents.
What can I use HSA or FSA funds for?
Both cover IRS-qualified medical expenses (doctor visits, prescriptions, many over-the-counter items, dental, vision, and more) — the qualifying expense list is largely the same for both account types.
Does contributing to an HSA reduce my paycheck by the full contribution amount?
No — because it's pre-tax, the actual reduction in your take-home pay is smaller than the contribution amount, similar to how a traditional 401(k) contribution works; see the Take-Home Pay After Benefits Calculator for that full breakdown.
What is the HSA catch-up contribution?
If you're 55 or older, you can contribute an extra $1,000 above the standard HSA limit for 2026 — this calculator applies it automatically when you check the age 55+ box.
Does this calculator account for employer contributions to my HSA?
Not separately — if your employer contributes to your HSA, that amount counts toward the same annual limit as your own contributions, so include it in your total desired contribution figure if applicable.
Can I share my HSA vs FSA comparison as an image?
Yes — tap Share and, on supported devices, your result is shared as a branded image card, not just a text link.
References
Important Information
This calculator provides estimates for informational purposes only and is not tax, legal, or financial advice. Uses 2026 IRS HSA and FSA limits; actual FSA carryover/grace-period rules are set by your specific employer plan and may differ from the maximum modeled here. Confirm your plan's specific rules with your benefits department.
Last updated: August 2026