US HSA vs FSA Calculator: Tax Savings on Health Costs

HSA or FSA: tax savings and forfeiture risk worked out

For every dollar paid into a US HSA or FSA through payroll, the tool counts a saving equal to your federal marginal rate plus your state rate plus 7.65% of FICA. It caps contributions at the 2026 IRS limits (HSA: $4,400 self-only, $8,750 family, plus $1,000 from age 55; FSA: $3,400) and works out how much of the FSA is lost at year end beyond the $680 carryover.

The calculation

• Savings rate = federal rate + state rate + 7.65% (FICA, when paid through payroll).
• HSA gain = capped HSA contribution × rate; FSA gain = capped FSA contribution × rate − FSA forfeited.
• FSA forfeited = FSA contribution − planned medical spending − $680 carryover, if positive.
• Projection: the HSA contribution invested each year at your chosen return, tax-free, against a brokerage account funded with the same contribution after tax and with its return cut by 15%.

Example

Age 32, self-only coverage, 24% federal bracket, 5% state tax, payroll contributions: combined rate 36.65%. A $4,400 HSA saves $1,613 in tax and a $3,400 FSA $1,246. With $1,200 of medical spending, $2,200 is left in the FSA: $680 carries over and $1,520 is lost, so the net FSA gain shown is $1,246 − $1,520 = −$274. Invested at 7.5% for 20 years, the HSA reaches $204,831 against $113,573 in a brokerage account.

Assumptions and limits

The tool does not check HSA eligibility, which requires a high-deductible health plan (HDHP) and no general-purpose FSA; a limited-purpose FSA (dental, vision) remains compatible. The FSA gain shown deducts the forfeited part, but not the $680 carried over, which is meant to be spent the following year. The $680 carryover exists only if the plan offers it; it may offer a 2½-month grace period instead. The projection assumes you pay medical bills out of pocket and make no withdrawals. Some states do not allow the HSA deduction. This is a tax estimate, not advice from a professional. To project an existing HSA balance with employer contributions, use the site's HSA investment calculator.

Sources and dates: IRS, Rev. Proc. 2025-19: HSA limits of $4,400 and $8,750 for calendar year 2026; IRS, Rev. Proc. 2025-32: $3,400 health FSA limit and $680 carryover for tax years beginning in 2026; IRS, Publication 969: $1,000 catch-up from age 55, grace period or carryover at the plan's choice, limited-purpose FSA (checked 14/10/2026).

Frequently Asked Questions

What are the HSA and FSA limits for 2026?

For 2026 the IRS sets the HSA limit at $4,400 for self-only coverage and $8,750 for family coverage, plus $1,000 from age 55 (Rev. Proc. 2025-19). The health FSA is capped at $3,400 of salary reductions, with a maximum carryover of $680 (Rev. Proc. 2025-32). Employer contributions count toward the HSA limit.

What happens to unspent FSA money?

It is lost at year end unless the plan offers a carryover ($680 at most in 2026) or a 2½-month grace period, one or the other. With $3,400 contributed and $1,200 spent, $680 rolls into next year and $1,520 is forfeited.

Can I have an HSA and an FSA at the same time?

Not with a general-purpose health FSA, which makes you ineligible for an HSA. A limited-purpose FSA covering dental, vision and preventive care remains compatible according to IRS Publication 969. You can then use both limits.

How much tax does an HSA save?

Your federal marginal rate plus your state rate, plus 7.65% of FICA if you contribute through payroll. With 24% and 5%, a $4,400 contribution saves $1,613; without payroll deduction the saving falls to $1,276 because there is no FICA exemption.

Is this tool really free?

Yes, all tools on Kristools are 100% free and accessible without registration.

Is my data protected?

Yes. All processing is performed directly and securely inside your browser. No personal data is sent to our servers.