HSA Contribution Limit Calculator
Your coverage through the year, your age, and what has gone in
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Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Educational estimate only. Confirm the assumptions, current rules, fees, and rounding that apply to your situation before making a decision.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter the months of 2026 you were covered by a qualifying high-deductible plan on the FIRST day of the month. Eligibility is tested monthly, and a plan that started on 2 June does not make June an eligible month.
- 02
Set the coverage type — 0 for self-only, 1 for family — and your age at the end of the year, which is what decides the $1,000 catch-up rather than your age when you contributed.
- 03
Enter any months covered by Medicare or another disqualifying plan. The page places these at the end of the year, because Medicare does not stop once it starts.
- 04
Answer the 1 December question honestly. If you were an eligible individual that day the last-month rule may give you the whole annual limit, but it attaches a testing period that runs to the end of the following year.
- 05
Add what you and your employer have already contributed, and what a spouse will put in their own HSA. Then read the month-by-month schedule, which runs the calculation the way the Line 3 worksheet in the Form 8889 instructions does.
Formula
Eligibility is monthly, so the limit is built a month at a time: Monthly limitation = (annual limit for your coverage type + catch-up if you are 55 or older at year end) ÷ 12 Month-by-month limit = Monthly limitation × eligible months Eligible months = months of qualifying high-deductible coverage on the first of the month, less any month enrolled in Medicare or other disqualifying coverage. The statute then offers a second route: Limit = the greater of (Month-by-month limit, full annual limit for the coverage held on 1 December) The second route is only available if you were an eligible individual on 1 December, and it carries a testing period to 31 December of the following year. The amount at risk is the difference between the two routes; failing the test adds that amount to income plus a 10% additional tax. For family coverage the base limit is shared with a spouse, while the catch-up is not: Your limit = (shared base − spouse's contribution) + your own catch-up Still available = your limit − your contributions − employer contributions Excess = contributions above the limit, taxed at 6% for each year it remains. 2026 figures: $4,400 self-only, $8,750 family, $1,000 catch-up from 55 (Rev. Proc. 2025-19 §2.01).
Example
Take seven months of family high-deductible coverage in 2026, age 58 at the end of the year, no Medicare, still eligible on 1 December, with $3,000 contributed by you, $1,200 by your employer and $2,000 going into a spouse's own HSA. The monthly limitation is the $8,750 family limit plus the $1,000 catch-up, divided by 12, or $813 a month. Seven eligible months — June through December on the page's schedule — come to $5,688. Against that, the full-year amount for December's coverage is $9,750. Because you were eligible on 1 December the greater figure wins, so the limit before any split is $9,750, and the last-month rule is worth $4,063 more than the monthly route. That extra is conditional: lose eligibility before 31 December 2027 and it becomes income plus a 10% additional tax of $406. The spouse's $2,000 comes out of the shared $8,750 base, leaving $6,750 for you, and your $1,000 catch-up sits on top, giving a final limit of $7,750. With $4,200 already in, $3,550 of room is left and there is no excess. Two alternates show the range: twelve months of self-only coverage at 40 gives a clean $4,400, or 12 × $367, with $200 of room left against the same $4,200; and turning 65 in July with six months of Medicare gives just $2,700, or 6 × $450, with the last-month rule unavailable because Medicare covered December — leaving a $1,500 excess and a $90 excise tax for each year it stays.
Definitions
- Eligible individual
- Someone covered by a qualifying high-deductible plan on the first day of a month, with no disqualifying coverage. Only eligible individuals may contribute to an HSA, and eligibility is tested month by month.
- Last-month rule
- A rule treating anyone eligible on the first day of the last month of the tax year — 1 December for most people — as eligible for the entire year, which can raise a prorated limit to the full annual one.
- Testing period
- For the last-month rule, the span from that December to the last day of the twelfth month following it. Losing eligibility within it adds the extra contribution to income and charges a 10% additional tax.
- Catch-up contribution
- An extra $1,000 a year for anyone 55 or older at the end of the tax year. It is per person, it is prorated with the rest when the limit is computed monthly, and each spouse must make it to their own HSA.
- Excess contribution
- Anything contributed above the limit, by you or your employer. It is not deductible and carries a 6% excise tax for each year it stays in the account, unless withdrawn with its earnings by the return's due date.
Good to know
Why the limit is not simply the annual figure
Almost everyone knows the headline HSA numbers: $4,400 for self-only coverage and $8,750 for family coverage in 2026, plus a $1,000 catch-up from age 55 (Rev. Proc. 2025-19 §2.01). Far fewer know those figures belong to a full year of eligibility, and that eligibility is tested month by month. You are an eligible individual for a month only if you were covered by a qualifying high-deductible plan on the first day of that month and had no disqualifying coverage. A plan that starts on 2 June does not make June an eligible month. Publication 969 sets out what happens when the year is not a clean twelve months: the limit becomes the greater of two figures. The first is the month-by-month total from the Line 3 Limitation Chart in the Form 8889 instructions, which adds a twelfth of the annual limit for each eligible month. The second is the full annual limit for whichever coverage you held on the first day of the last month of the year. The page computes both and takes the larger, exactly as the worksheet does. On the example — seven months of family coverage at age 58 — the monthly route gives $813 a month for seven months, or $5,688, while the full-year figure including catch-up is $9,750. The second is larger, so it stands. Change the facts slightly and the answer changes completely: twelve months of self-only coverage at age 40 gives a flat $4,400, or twelve months at $367. The lesson is that there is no single right answer to what you may contribute until the calendar is settled, which is why the page asks for months rather than for a yes or no.
The last-month rule and the testing period attached to it
The second branch of the greater-of test exists because of the last-month rule, and it is generous. If you are an eligible individual on the first day of the last month of your tax year — 1 December for almost everyone — Publication 969 treats you as eligible for the entire year, and you are treated as having the same coverage all year as you had that day. Someone who takes a new job with a high-deductible plan in June can therefore contribute the whole annual limit rather than seven twelfths of it. On the page's example that is worth $4,063 more than the monthly route. The generosity comes with a condition that catches people out a year later. If contributions were made on the strength of the last-month rule, you must remain an eligible individual throughout a testing period that begins with that December and ends on the last day of the twelfth month following it — December 2026 through 31 December 2027 for the 2026 tax year. Fail it for any reason other than death or becoming disabled and the contributions you would not have been allowed to make without the rule are added to your income in the year you fail, plus a 10% additional tax, worked out on Form 8889 Part III. On the example the amount exposed is $4,063 and the additional tax alone is $406, on top of income tax at whatever rate applies then. This matters most to people who can foresee the disqualifying event: someone planning to retire and start Medicare during the following year, or expecting to move to a spouse's traditional plan. For them the safe course is to contribute only the month-by-month amount, $5,688 here, and keep the certainty. The page shows both figures side by side for exactly this decision.
Medicare, retroactive Part A, and the six-month warning
Nothing ends HSA eligibility as completely as Medicare. Publication 969 is blunt: beginning with the first month you are enrolled in Medicare, your contribution limit is zero. There is no partial treatment and no exception for someone still working and still covered by an employer's high-deductible plan. Enrolment alone does it, and Part A by itself is enough. What turns this from a rule into a trap is the retroactive start. According to medicare.gov, premium-free Part A signed up for after you turn 65 begins six months back from when you sign up, or from when you apply for benefits from Social Security or the Railroad Retirement Board, though never earlier than the month you turned 65. Publication 969 confirms that the zero-contribution rule applies to periods of retroactive coverage, so contributions made during those backdated months become excess contributions after the fact. Someone who contributes all year and then claims Social Security in November can find that the previous six months were never eligible. Medicare's own guidance says as much, advising people to stop HSA contributions at least six months before applying. The page models this by placing Medicare months at the end of the year, because Medicare does not stop once it starts, and by refusing to apply the last-month rule when Medicare covers December — you cannot be an eligible individual on 1 December while enrolled. The alternate scenario on the page shows the shape of it: someone who turned 65 in July with six months of Medicare has six eligible months of self-only coverage, $450 a month, giving a limit of $2,700 rather than the $5,400 full-year figure. Against $4,200 already contributed that leaves a $1,500 excess and a $90 excise tax for every year it stays in the account.
Spouses, the catch-up, and getting an excess back out
Two rules about couples cause most of the remaining confusion. The first is that family coverage buys one limit, not two. Publication 969 says that if either spouse has family coverage both are treated as having it, and the single family limit is divided equally between them unless they agree on a different split. On the example the shared base is $8,750, so a spouse putting $2,000 into their own account leaves $6,750 for you. Couples who each open an HSA and each contribute the full family limit are making a large excess contribution between them. The second rule runs the other way: the catch-up is personal. Publication 969 states that where both spouses qualify, each must make the additional contribution to their own HSA. It cannot be doubled into one account or transferred to a spouse, which means a couple who both qualify need two accounts to collect both. On the example the $1,000 catch-up sits on top of the $6,750 share, giving $7,750. Note too that the catch-up is prorated along with everything else when the limit is computed monthly — the Medicare alternate shows $500 of catch-up rather than $1,000, because only six months were eligible. Employer contributions complicate the count without changing the rules. Anything an employer puts in, including money routed through a cafeteria plan, reduces what you may add, which is the usual reason a return ends up reporting an excess that nobody meant to make. If it happens, the fix is time-limited but real. Excess contributions are not deductible and carry a 6% excise tax for each year they remain, reported on Form 5329. Withdraw the excess together with the net income earned on it by the due date of your return, including extensions, and the excise tax does not apply to the amount withdrawn. Leave it and the 6% is charged again every year.
Frequently asked questions
How is the HSA limit prorated for a partial year?
Publication 969 gives the limit for a part-year as the greater of two figures: the month-by-month total from the Line 3 Limitation Chart, or the full annual limit for the coverage you held on the first day of the last month. On the page's example — seven eligible months of family coverage at age 58 — the monthly route gives 7 × $813, or $5,688, while the full-year figure is $9,750. Because the visitor was eligible on 1 December, the larger figure stands. The page always computes both and takes the greater.
What is the last-month rule, and what is the catch?
If you are an eligible individual on 1 December you are treated as eligible for the whole year, which on the example lifts the limit from $5,688 to $9,750 — $4,063 more. The catch is the testing period. Publication 969 requires you to remain eligible from that December through the last day of the twelfth month following it, so December 2026 to 31 December 2027. Fail that, for any reason other than death or disability, and the $4,063 goes into your income for the year you fail, plus a 10% additional tax of $406, worked out on Form 8889 Part III.
Does Medicare stop me contributing to an HSA?
Yes, completely, from the first month you are enrolled. Publication 969 states that beginning with that month your contribution limit is zero, and that the rule applies to periods of retroactive coverage. This is where people are caught out: medicare.gov says premium-free Part A signed up for after 65 starts six months back from when you sign up or apply for Social Security, never earlier than the month you turned 65. Medicare's own guidance therefore tells people to stop HSA contributions at least six months before applying.
What happens if I contribute too much?
Excess contributions are not deductible and carry a 6% excise tax for each year they stay in the account, reported on Form 5329. Rerunning the page for someone who turned 65 in July with six months of Medicare gives a limit of $2,700 against $4,200 already contributed — an excess of $1,500 and a $90 excise tax every year it remains. There is an escape: withdraw the excess along with the net income earned on it by the due date of your return including extensions, and the excise tax does not apply to what you withdrew.
Can my spouse and I each contribute the family limit?
No. Publication 969 says that if either spouse has family coverage both are treated as having it, and the single family limit is split equally between you unless you agree on a different division. On the example the shared base is $8,750; a spouse contributing $2,000 to their own account leaves $6,750 for you. The catch-up is the exception — it is personal, and each spouse must make it to their own HSA, so it sits on top of your share rather than inside it.
Is the $1,000 catch-up prorated too?
Yes, when the limit is computed month by month. Publication 969's own example is a person who turned 65 in July with self-only coverage and catch-up eligibility, whose limit is the annual figure including catch-up multiplied by 6 ÷ 12. The page does the same: on the Medicare alternate, six eligible months of self-only coverage at age 65 give $450 a month, or $2,700, of which $500 is catch-up. Under the last-month rule the full $1,000 is available instead.
Do my employer's contributions count against my limit?
Yes, and so does anything anyone else puts in on your behalf. Publication 969 requires you to reduce what you can contribute by any employer contributions excludable from your income, including money routed through a cafeteria plan. On the example, $3,000 of your own plus $1,200 from your employer is $4,200 against a $7,750 limit, leaving $3,550. A forgotten payroll contribution is the usual way a return ends up reporting an excess.