A Health Savings Account is the most tax-efficient account most people underuse. It is the only account that is untaxed at all three stages — going in, growing, and coming out for medical costs. This calculator turns that abstract benefit into two concrete numbers: the tax you save each year, and how large the balance grows by retirement if you invest it.

The triple tax advantage, and the payroll bonus

Three tax breaks stack inside an HSA. First, contributions are deductible at your combined federal and state rate, so a $4,400 contribution at a 29% combined rate saves about $1,276 in tax the year you make it. Second, growth is never taxed — no annual drag on dividends or capital gains, so the balance compounds like a Roth. Third, qualified medical withdrawals are tax-free, forever. If you contribute through payroll, a fourth break applies: those dollars also escape the 7.65% FICA payroll tax, which no other retirement account can do.

Why 'invest and pay cash' wins

The single biggest HSA move is to invest the balance and pay current medical bills from other cash, keeping receipts. Because qualified reimbursements have no deadline, you can pay yourself back years or decades later — tax-free — while the money compounds in the meantime. In the calculator's example, paying $1,500 a year of medical costs from cash instead of the HSA leaves roughly $95,000 more in the account by age 65. The gap is entirely tax-free growth on dollars you chose not to withdraw. This only works if you can comfortably cover current medical costs from cash; if you can't, spending from the HSA is exactly what it's for.

Limits, eligibility, and what happens at 65

You can only contribute if you have an HSA-eligible HDHP, and contributions stop once you enroll in Medicare. The 2026 limits are $4,400 self-only and $8,750 family, plus a $1,000 catch-up at 55 and older. A few states (notably California and New Jersey) tax HSA contributions, so set the state rate to 0 there. At age 65, the HSA becomes even more flexible: you can withdraw for any reason without the 20% penalty — non-medical withdrawals are simply taxed as ordinary income, exactly like a traditional IRA, while medical withdrawals stay tax-free. This is an educational estimate that assumes a constant return and tax rate; real returns vary and tax law changes.