HSA Calculator

How HSA growth and the triple tax advantage are calculated

The balance is a plain future-value calculation with contributions added at the end of each year. What makes an HSA an HSA isn't the compounding — it's that no tax is levied at any of the three points where other accounts take a bite.

The tax saving is calculated separately and deliberately kept out of the balance. Your deduction is money that stays in your pocket in April, not money that lands in the account — so adding it to the projection would be double-counting.

cap = (4,400 self-only | 8,750 family) + (1,000 if age 55+) contrib = min(your contribution, cap) balance = starting balance × (1 + return) ^ years + contrib × ((1 + return) ^ years − 1) ÷ return tax saved per year = contrib × marginal rate growth = balance − starting balance − contrib × years

cap

The 2026 HSA contribution limit for your coverage — $4,400 self-only, $8,750 family, plus a $1,000 catch-up from age 55 (IRS Rev. Proc. 2025-19)

contrib

What actually goes in each year — your figure, capped — the slider can't exceed the limit

starting balance

What your HSA holds today — compounds for the whole horizon

return

Expected annual return on the invested portion — most HSAs hold a cash floor that earns far less — see the limitations

years

How long you leave it alone — the model assumes no withdrawals at all across the horizon

marginal rate

Your combined federal and state rate, for valuing the deduction — HSA contributions through payroll also escape FICA — this model doesn't count that

growth

Compounding, net of what you and your balance put in — tax-free if withdrawn for qualified medical expenses

The triple advantage is genuinely unique in the US code — no other account is untaxed going in, growing and coming out. A 401(k) gives you the first two; a Roth gives you the last two. But the third leg has a condition attached, and the condition is that the money leaves for qualified medical expenses. The model assumes it does. It also assumes you're eligible to contribute for all 20 years, which requires being covered by a qualifying high-deductible health plan the entire time — a status this calculator never checks. For the workplace comparison, see the 401(k) calculator.

Worked examples

Frequently asked questions

What this HSA calculator doesn't check

The compounding is straightforward. Eligibility — which is the hard part of an HSA in practice — is entirely absent from the model.

• Whether you're eligible at all — Contributing requires coverage under a qualifying high-deductible health plan, with no other disqualifying coverage. The calculator never asks, and the HDHP deductible and out-of-pocket thresholds that define "qualifying" aren't in our data module — check IRS Rev. Proc. 2025-19 for the 2026 figures.
• Medicare ends contributions — The model will happily project 40 years of deposits from any starting point. Enrolling in Medicare stops eligibility, which for most people means contributions end around 65 — well before a long projection assumes.
• The cash floor — The return is applied to the whole balance. Most HSA providers require a minimum in cash before you can invest, and that portion earns close to nothing — so a real account compounds a bit slower than the projection.
• It assumes you never spend it — Not a dollar comes out across the horizon. An HSA used as a health account — paying this year's costs from this year's contributions — never builds the balance shown here, and that's the ordinary way to use one.
• The deduction is undercounted — Tax saved is contribution × marginal rate. Contributions made through payroll also escape Social Security and Medicare tax, which no other retirement account allows and this model doesn't credit — so the real saving is larger than $720.
• Non-medical withdrawals before 65 — The balance is labelled tax-free, which holds only for qualified medical expenses. Take it for anything else before 65 and it's ordinary income plus a 20% penalty — double the 401(k) penalty.