HSA Calculator: Health Savings Account Growth Projector

Disclaimer: This calculator is provided for educational and estimation purposes only and does not constitute formal financial or tax advice. HSA rules change; confirm current contribution limits and qualified expenses with the IRS or a tax professional.

What this calculator actually answers

“Where will my HSA actually be at retirement?” is a question most people never run the numbers on, because the account is usually introduced as a healthcare convenience rather than what it really is: the only account in the US tax code with the full triple tax advantage.

• In: contributions go in pre-tax through payroll (skipping federal income tax and FICA), or are income-tax-deductible if you fund the account yourself.
• Growth: the balance compounds with no tax ever assessed on the gains.
• Out: withdrawals for qualified medical expenses are completely tax-free — at any age, with no time limit on reimbursement.

Compare that with the 401(k) calculator’s account: pre-tax in, taxed on the way out — two benefits. The Roth vs. Traditional IRA calculator’s Roth: taxed on the way in, tax-free out — two benefits. The HSA is the only one where all three legs apply, which means the same pre-tax dollar goes further in an HSA than in either. This calculator runs your actual numbers — contribution, employer money, medical spending, return — through a 35-year compounding projection and shows you what that difference is worth.

The tax mechanics that make it work

The three legs have two conditions attached. You must be enrolled in a qualifying high-deductible health plan (HDHP) to contribute, and you cannot be on Medicare. Withdrawals are tax-free only for qualified medical expenses — deductibles, copays, dental, vision, and most out-of-pocket care. Anything else before 65 is taxed plus a 20% penalty; after 65 the penalty falls away and income tax alone applies.

Because the account is owned by you, not your employer, it is portable between jobs, and — unlike a 401(k) — it has no required minimum distributions at any age. The balance can keep compounding for your whole life, which is why the FIRE calculator crowd treats the HSA as a stealth retirement account: healthcare is one of the largest and most unpredictable retirement expenses, and this is the only vehicle designed to pay it with tax-free money.

The 2026 contribution limits

The IRS sets a dollar cap each year, adjusted for inflation. For 2026:

The “against the limit” row matters more than people expect: a $1,000 employer contribution does not add room, it consumes it, leaving $3,400 of your own $4,400 under self-only coverage. The calculator treats your contribution and the employer’s as separate inputs because the employer money is still your balance — but the two together are what the IRS caps.

The projection math

The projection is the standard monthly-compounding recurrence used across this site: a starting balance $P$ earning $r/12$ per month, with a net monthly deposit $M$ added at the end of each month for $n$ months:

$$FV = P\left(1 + \frac{r}{12}\right)^n + M \times \frac{\left(1 + \frac{r}{12}\right)^n - 1}{r/12}$$

For the HSA, the net deposit is what goes in minus what comes out for healthcare:

$$M = \frac{\text{annual contributions} + \text{employer contributions} - \text{annual medical costs}}{12}$$

with one honest constraint: the account cannot be overdrawn, so the projection floors the balance at zero when medical spending outruns contributions and growth. The real (today’s-dollar) figure deflates each month’s balance by cumulative inflation, exactly as the 401(k) calculator does.

The defaults tell the real story

Run the defaults — a 30-year-old with $5,000 already saved, contributing the 2026 self-only limit of $4,400 a year, a $1,000 employer contribution, 7% return, 3% inflation, and no medical spending out of the account:

The headline is the ratio, not the balance: of the $868,005, only $194,000 was ever put in. $674,005 — 78% of the final figure — is tax-free growth. That is the third leg of the advantage doing the heavy lifting, and it is why starting early dominates every other dial.

The dial that matters most: medical spending

The one decision that separates an HSA from every other retirement account is what you do with current medical bills. Spending from the account stops that money from compounding — permanently. Keeping the same receipts and paying the bills from other money (the invest-and-reimburse strategy) lets the full balance work, and the IRS puts no time limit on when you can reimburse yourself, as long as the expense was incurred while covered by an HDHP.

Paying $1,500 a year of healthcare from the account — roughly the average deductible-era out-of-pocket spend — costs you $225,131 of retirement balance, a quarter of a million dollars surrendered to current-year bills. The money is not lost forever; it just stops growing. The strategy, then, is a cash-flow question first: if you can cover the bills out of pocket and file the receipts, the account’s growth is the prize. If the balance would drain — run $9,000 a year on the defaults and the projection hits zero in month 18 — the honest answer is that the account cannot fund your healthcare alone, and spending from it is unavoidable.

The dials that matter second

The return assumption moves the outcome more than the contribution rate, just as it does for the 401(k) calculator:

And starting age is the dial nobody can change retroactively:

A 50-year-old maxing the account still ends with about a third of the 30-year-old’s balance in real terms — not because the contribution differs, but because the growth leg has no time to run. The employer contribution matters too: drop the $1,000 employer money from the defaults and the balance falls to $717,917, a reminder that free money left on the table costs more than the nominal amount, because it never compounds.

Where the assumptions break

• Static contributions. The model holds your annual contribution flat for the whole horizon. In reality the IRS raises the limit most years, and most savers contribute more as income rises — the projection understates the outcome for anyone who stays eligible.
• A static rate. One return for 35 years, no sequence-of-returns risk. As the return table shows, this single assumption dominates the result; use an after-fee, after-tax-expected figure and treat the high and low columns as the plausible band.
• No tax modeling beyond the account itself. The balance is pre-tax money compounding tax-free. Direct (non-payroll) contributions are deductible but not FICA-exempt, and payroll contributions skip FICA entirely — neither saving is counted here, so the real advantage is larger than shown, not smaller.
• The penalty scenario is not modeled. The calculator assumes every withdrawal is a qualified medical expense. A non-medical withdrawal before 65 would be taxed and penalized 20% on top, which the chart would not show.
• The rules are not permanent. Limits, HDHP definitions, and the penalty structure have all changed before and will change again. Re-run the projection with current numbers, and confirm eligibility with a tax professional rather than assuming a plan qualifies.

None of these make the projection wrong; they make it a planning tool with honest inputs. The value is in seeing what the third leg is worth before it is spent — the same reason the inflation-adjusted savings goal calculator exists for targets that move with prices.

How to use this calculator

• Current age picks where the projection starts. The earlier the start, the more the growth leg does — see the starting-age table above.
• Retirement age sets where the balance stops growing and the projection ends. Because an HSA has no RMDs, this is the age you plan to start spending the money, not a legal deadline.
• Your annual contribution is what you set aside each year, up to the 2026 limit in force for your coverage type. The 50/30/20 budget calculator is where to find a figure you can sustain.
• Employer contribution is the flat annual amount your employer funds, typically $500–$1,000. It counts against the same IRS limit.
• Current balance is what the account holds today, including any employer money already vested.
• Medical costs paid from HSA is the annual qualified spending you actually draw from the account. $0 models the invest-and-reimburse strategy and shows the maximum growth; enter real spending to see how much of the third leg it costs.
• Expected return is the after-fee nominal rate you expect on the account’s investments. 7% is the historical ballpark for an equity-heavy portfolio; use 5% for a conservative check and 9% for an optimistic one.
• Inflation deflates the final balance to today’s dollars. 3% is the long-run average; the real figures are the ones that compare honestly against today’s prices.

The account’s whole case rests on one sentence: pre-tax in, tax-free growth, tax-free out. This calculator exists to show you what that sentence is worth in dollars — and how quickly medical spending spends it.