FSA & Commuter Benefits Calculator

Enter your salary, filing status, expected health FSA election, medical spending, and monthly transit and parking costs to see how much federal income tax, payroll tax, and (optionally) state tax the pre-tax elections save, and how much of the FSA could be forfeited.

Short answer: every dollar you run through a health FSA or a pre-tax commuter benefit skips federal income tax at your marginal rate and the 7.65% Social Security and Medicare tax. At the 22% bracket that's 29.65 cents per dollar: the 2026 maximum health FSA of $3,400 saves $1,008.10, and the maximum $340 a month for transit saves another $1,209.72, before state tax.

The calculator is for informational purposes only, and its results are estimates; your W-2 and tax return determine the real savings. For the plan rules behind these numbers (eligible expenses, carryover and grace periods, dependent care FSAs, and open enrollment strategy), read the FSA and commuter benefits tax savings guide.

What do you enter in the FSA and commuter calculator?

You don't need to look up your bracket: the tool figures it from your salary using the 2026 brackets in Rev. Proc. 2025-32 and the standard deduction ($16,100 single, $32,200 joint).

How does the calculator figure your tax savings?

It adds three pieces:

1. Federal income tax: tax on (salary − standard deduction) minus tax on (salary − pre-tax elections − standard deduction). If the elections straddle a bracket line, each part is taxed at its own rate.
2. FICA: employee Social Security and Medicare on your salary minus the same on your salary after the elections. Social Security (6.2%) only applies up to the $184,500 wage base for 2026, so above it you save only Medicare — 1.45%, plus the 0.9% Additional Medicare tax on wages over $200,000.
3. State tax: pre-tax total × the state rate you enter.

The total is then split between the health FSA and the commuter benefits in proportion to the dollars in each.

2026 vs 2025 limits used by the tool

How the "FSA money at risk" figure works

• Use-it-or-lose-it: at risk = election − expected expenses.
• Carryover: at risk = election − expected expenses − $680 (2026). Anything within the carryover rolls into next year instead of being lost.
• Grace period: the tool uses the same formula as use-it-or-lose-it and reminds you that expenses in the grace period count. A grace period of up to 2½ months gives you more time to incur expenses, which lowers the real risk if you have spending you can schedule in January through mid-March, but money still unspent after the grace period is forfeited.

Worked example: the default scenario

Single, $85,000 salary, $3,000 health FSA election, $2,500 of expected medical costs, plan with carryover, $200 a month transit, $150 a month parking, state rate left at 0.

Add your state rate and the tool adds it: at 5%, $7,200 × 5% = $360, for a total of about $2,495. Check your state's rules first; most states with a wage tax follow the federal exclusion, but not every state does for every benefit.

Change the plan type to use-it-or-lose-it and the at-risk figure becomes $3,000 − $2,500 = $500. If that $500 is forfeited, you saved $500 × 29.65% = $148.25 in tax on it but lost the $500 itself, a net loss of $351.75. That's why the election should track predictable spending, not a best-case guess.

How much should you elect? The break-even rule

Each marginal FSA dollar either gets spent (you gain your tax rate) or gets forfeited (you lose the dollar minus the tax you saved on it). The break-even probability of spending that dollar is 1 minus your combined tax rate:

Add your state rate to the combined rate for a more precise threshold. In practice, start from costs you can document (recurring prescriptions, scheduled orthodontic payments, glasses every year, a planned procedure) and stop there. If your plan offers a carryover, the first $680 of overshoot isn't at risk, so you can elect a little above your documented costs.

Worked example: a higher earner above the wage base

Single, $250,000 salary, maximum health FSA ($3,400), $340 a month transit ($4,080 a year), no parking. Pre-tax total: $7,480.

• Federal: taxable income falls from $233,900 to $226,420, all inside the 32% bracket ($201,775–$256,225): $7,480 × 32% = $2,393.60
• FICA: wages stay above the $184,500 Social Security wage base, so Social Security doesn't change. Medicare and Additional Medicare (wages are over $200,000) fall by $7,480 × (1.45% + 0.9%) = $175.78
• Total the calculator shows: $2,569.38, split $1,167.90 FSA and $1,401.48 commuter

A flat "marginal rate + 7.65%" rule of thumb would claim $2,966 here — about $397 too much — because it charges Social Security on wages the 6.2% no longer reaches.

Worked example: a lower earner

Single, $40,000 salary, $1,000 health FSA, $100 a month transit. Taxable income of $23,900 is in the 12% bracket.

• Pre-tax total: $1,000 + $1,200 = $2,200
• Savings: $2,200 × (12% + 7.65%) = $2,200 × 19.65% = $432.30

At lower incomes the FICA piece is a bigger share of the benefit: here $168.30 of the $432.30 comes from Social Security and Medicare. One small trade-off: Social Security wages are lower by the same $2,200, which slightly reduces the earnings record your future benefit is based on.

What the calculator doesn't model

• Local income tax, and state tax beyond the single rate you enter.
• Itemized deductions and other income. The federal saving assumes salary is your only income and you take the standard deduction; other income can put you in a higher bracket.
• Costs above the commuter cap. If parking costs $400 a month, the tool counts $340; the extra $60 is paid with after-tax money (or, if your employer pays it, the excess is added to your taxable wages).
• Employer contributions. Some employers add money to the health FSA or pay for transit outright. Employer-paid amounts are tax-free to you within the same limits, so they're worth more than the tool's salary-reduction math suggests.
• Dependent care FSA. It also avoids income tax and FICA, but with a $7,500 limit for 2026 and different rules; see the guide linked above.
• HSA interaction. If you're enrolled in an HSA-qualified high-deductible health plan, a general-purpose health FSA generally blocks HSA contributions. A limited-purpose (dental and vision) FSA doesn't. Compare the two with the HSA calculator, which uses the 2026 HSA limits of $4,400 self-only and $8,750 family.

Common mistakes when using the results

• Entering your effective state rate instead of your marginal rate. Savings come off the top of your income, so use your state's bracket rate, not total state tax ÷ income.
• Counting commuter costs you won't have. Remote or hybrid days reduce transit use; elect for the months and days you'll actually commute, and change the election when that changes (commuter elections are usually changeable monthly, unlike FSA elections).
• Treating parking near your home as eligible. Qualified parking must be at or near your work or near the place you board transit, vanpool, or carpool to work.
• Expecting a bike commuting benefit. The qualified bicycle commuting reimbursement exclusion was eliminated permanently for tax years beginning after 2025, so employer bike reimbursements are now taxable wages.
• Forgetting the savings shows up in each paycheck, not at tax time. You won't see a line for it on your return; it's already reflected in lower W-2 box 1, 3, and 5 wages.

See the effect on your paycheck

Pre-tax elections change each paycheck before withholding is figured. To see that step in context, follow how to calculate your paycheck after taxes or run the paycheck after-tax calculator with and without the elections. For every 2026 benefit limit in one place, see the 2026 IRS inflation adjustments guide.