FSA Tax Savings Calculator

Introduction: what an FSA actually saves you

A health Flexible Spending Account (FSA) lets you pay eligible medical costs with pre-tax payroll deductions. Money is redirected out of your pay before three separate taxes are computed: federal income tax, state income tax, and employee FICA. That third one is the piece most calculators get wrong, because the FICA saving is not a flat 7.65 % for everyone — it depends on where your FSA dollars sit relative to the Social Security wage base and the Additional Medicare Tax threshold.

This calculator uses the gross income you enter to work that out properly, rather than assuming the same payroll rate applies whether you make $50,000 or $300,000. For a high earner electing the 2026 maximum, the difference between the flat assumption and the correct marginal treatment is roughly $180 of imaginary savings.

It also answers the question most people actually have at open enrollment, which is not “how much will I save?” but “how much can I safely elect given I might not spend it all?” Because the tax saving comes off the top, there is a break-even amount of forfeiture you can absorb and still come out ahead of paying cash. The calculator reports that number in dollars.

How to use the FSA tax savings calculator

• Annual gross income now does real work: it determines your marginal payroll-tax rate. Enter your gross wages from this employer, before any deductions.
• Filing status sets the Additional Medicare Tax threshold — $200,000 for single and head of household, $250,000 married filing jointly, $125,000 married filing separately.
• Account type selects the right IRS cap for 2026: $3,400 for a health FSA, $7,500 for dependent care ($3,750 if married filing separately). The calculator flags an election above the cap rather than silently computing an impossible saving.
• Annual FSA election: the amount you will actually have deducted over the plan year. Enter what you expect to spend, not the maximum you could contribute.
• Federal and state tax rate: your marginal rates, meaning the rate that applies to your last dollars of income, not your average or effective rate. Fold local income tax into the state figure if you pay it.
• Pay periods per year converts the election into the per-paycheck deduction you will actually see on your payslip — 26 for biweekly, 24 for semi-monthly, 12 for monthly.

Press Calculate and the panel breaks the saving into its income-tax and payroll-tax components, reports the effective discount, the per-paycheck deduction, and the forfeiture break-even. The chart below redraws to show how much of your election is tax saving and how much is genuine out-of-pocket cost.

Formulas: income tax, marginal FICA, and the forfeiture break-even

The income-tax half is simple. With election , marginal federal rate and marginal state rate :

The payroll half is where care is needed. An FSA election reduces your taxable wages from down to , so the relevant question is which payroll taxes apply in that band. Social Security at 6.2 % only applies to the part of the band below the wage base :

Medicare at 1.45 % has no ceiling and applies to the whole election, while the 0.9 % Additional Medicare Tax applies only to the part of the band above the filing-status threshold :

so the payroll saving assembles from three pieces rather than one flat rate:

Total saving, effective discount and after-tax cost then follow directly:

The forfeiture break-even falls out of the same algebra. Electing and forfeiting of it costs you in take-home pay while buying of care. Paying cash for that same care costs . Setting the two equal:

In plain terms: you can forfeit up to your entire tax saving and still be no worse off than never having had the FSA. At a 34.65 % effective discount, a third of the election can go unspent before the arrangement turns negative. That is a far more useful planning number than the raw savings figure.

Worked example: two earners, same election

Case A — a $80,000 single filer electing $3,000. Marginal federal 22 %, state 5 %.

• Income tax saving: $3,000 × 0.27 = $810.00
• Social Security: the election band runs from $77,000 to $80,000, entirely below the $184,500 wage base, so all $3,000 qualifies → $3,000 × 0.062 = $186.00
• Medicare: $3,000 × 0.0145 = $43.50; Additional Medicare does not apply below $200,000
• FICA saving: $229.50, the familiar 7.65 %
• Total: $1,039.50, an effective discount of 34.65 %, leaving an after-tax cost of $1,960.50
• Forfeiture break-even: $1,039.50 — this employee could leave a third of the election unspent and still break even against paying cash

Case B — a $250,000 single filer electing the $3,400 maximum. Marginal federal 32 %, state 5 %.

• Income tax saving: $3,400 × 0.37 = $1,258.00
• Social Security: the band runs $246,600 to $250,000, entirely above the $184,500 wage base, so none of it escapes the 6.2 % → $0
• Medicare: $3,400 × 0.0145 = $49.30; the whole band sits above the $200,000 Additional Medicare threshold, so $3,400 × 0.009 = $30.60 also applies
• FICA saving: $79.90, a marginal 2.35 % rather than 7.65 %
• Total: $1,337.90, an effective discount of 39.35 %

A calculator assuming a flat 7.65 % would have quoted Case B $1,518.10, overstating the benefit by $180.20. The higher marginal income-tax rate more than compensates, so the FSA is still a better deal for the high earner — but not for the reason the flat model suggests.

Case C — straddling the wage base. An employee earning $186,000 electing $3,400 has a band from $182,600 to $186,000. Only $184,500 − $182,600 = $1,900 of it is below the wage base, so Social Security saves $1,900 × 0.062 = $117.80, Medicare adds $49.30, and the marginal FICA rate lands at 4.91 % — between the two clean cases and impossible to reach with a flat assumption.

FSA against paying out of pocket

The last row is the break-even. Below it the FSA wins; above it, cash would have been cheaper. Note that the take-home column never changes with forfeiture — the money left your paycheck either way — which is exactly why forfeiture feels worse than it costs.

2026 contribution limits and use-it-or-lose-it planning

For plan years beginning in 2026 the IRS health FSA salary-reduction limit is $3,400 (up from $3,300 in 2025), and plans offering a carryover may roll up to $680 of unused funds into the following year. Dependent-care FSAs rise to $7,500 for married filing jointly and single filers ($3,750 if married filing separately), the first increase in that cap in decades. Employers may set lower caps than the IRS maximums, and the health FSA limit is per employee — two working spouses can each elect up to the cap under their own employers’ plans.

Plans may offer either a carryover or a grace period of up to 2.5 extra months, never both, and some offer neither. Check which one your plan document specifies before deciding how aggressive an election to make, because a carryover protects a fixed dollar amount while a grace period protects an unlimited amount but only for a fixed window.

If your predictable expenses exceed the cap, the excess simply has no FSA discount available. Enter your election, not your total medical budget.

FSA or HSA: the one-paragraph comparison

If your employer offers a high-deductible health plan with an HSA, the comparison is worth a minute. An HSA offers the same pre-tax contribution benefit plus tax-free growth, no use-it-or-lose-it deadline, portability between jobs, and it also avoids FICA when funded by payroll deduction — but it requires HDHP coverage and you generally cannot hold a general-purpose health FSA alongside it (a limited-purpose dental and vision FSA is the usual pairing). The FSA’s unique advantage is the uniform coverage rule: your full annual election is available on day one of the plan year, even before you have contributed a cent of it, which is effectively an interest-free advance for January expenses.

Limitations and assumptions worth reading

• Marginal rates, not effective rates. The federal and state inputs must be the rates applying to your last dollars of income. Entering an average rate will understate the saving, sometimes badly.
• The income-tax side ignores bracket-straddling. If your election is large enough to drop you into a lower federal bracket partway through, the true saving is a blend of two rates. The payroll side handles its thresholds exactly; the income-tax side does not.
• Cafeteria plan assumed. The FICA exclusion depends on the deductions running through a Section 125 plan. Almost all employer FSAs do, but a handful of arrangements do not, in which case only the income-tax saving applies.
• Employer FICA is not counted. Your employer also saves 7.65 % on the same dollars. That is a real economic effect but it does not reach your pocket, so it is excluded here.
• State treatment varies. A few states do not conform to the federal cafeteria-plan exclusion, and some localities tax differently. Fold local income tax into the state input if it applies to you.
• Eligibility and substantiation. The saving only materialises if you actually spend the money on qualified expenses within your plan’s deadlines and can substantiate the claims.
• Not tax advice. This is an educational estimate. Your plan administrator or a tax professional should confirm anything you act on.

Sources. 2026 health FSA limit of $3,400 and $680 carryover: IRS Revenue Procedure 2025-32. 2026 Social Security taxable wage base of $184,500: Social Security Administration, Contribution and Benefit Base. FICA rates of 6.2 % Social Security and 1.45 % Medicare on the employee side, and the 0.9 % Additional Medicare Tax with thresholds of $200,000 single and head of household, $250,000 married filing jointly, $125,000 married filing separately: IRS Topic No. 751 and IRS Questions and Answers for the Additional Medicare Tax. Section 125 cafeteria plan treatment and the uniform coverage rule: IRS Publication 969. Last reviewed July 2026.

FSA questions employees ask at open enrollment