HSA Calculator

How the HSA calculator works

A health savings account is the only account that is tax-free three times: contributions are deducted, growth is not taxed, and withdrawals for qualified medical costs are tax-free. This HSA calculator starts from the 2026 limit for your coverage ($4,400 self-only, $8,750 family, plus $1,000 if you are 55 or older), subtracts what your employer puts in, and multiplies your own contribution by every tax it avoids: your federal bracket, your state rate and, when the money goes in through payroll, 7.65% Social Security and Medicare tax.

Worked example

A single filer earning $100,000 is in the 22% federal bracket after the $16,100 standard deduction. Putting the full $4,400 in through payroll with a 5% state tax saves $4,400 × 22% = $968 of federal tax, $220 of state tax and $4,400 × 7.65% = $336.60 of FICA, a total of $1,524.60. The same deposit made on your own, from your bank account, saves only $1,188, because FICA was already withheld from that pay. A family that contributes $8,750 every year and invests it at 6% would have about $321,874 after 20 years, all of it available tax-free for medical bills.

Who can contribute, and how much

You need a high-deductible health plan: for 2026 a deductible of at least $1,700 (self-only) or $3,400 (family) and out-of-pocket costs capped at $8,500 or $17,000. You cannot be on Medicare or have other non-HDHP coverage such as a general-purpose FSA. If you are eligible only part of the year, the limit is prorated by month, which the months field handles. The last-month rule lets you contribute the full year's amount if you are eligible on December 1, but you must then stay eligible through the following year or pay tax and a 10% penalty on the extra.

Common mistakes

Forgetting the employer's money is the classic one: if your employer adds $1,000, your own room on self-only coverage is $3,400, not $4,400. Contributions above the limit are taxed 6% a year until removed. Married couples with family coverage share one family limit. And in California and New Jersey the state taxes HSA contributions, so the real saving there is smaller; enter 0% as the state rate. Above the $184,500 Social Security wage base, payroll contributions save only the 1.45% Medicare tax.

Sources

IRS Rev. Proc. 2025-19 (2026 HSA and HDHP limits), IRS Publication 969 (HSA rules, last-month rule, excess contributions), IRS Form 8889 instructions, SSA 2026 contribution and benefit base ($184,500), IRS Rev. Proc. 2025-32 (2026 brackets and standard deduction).