How does the tax savings calculator work?

Enter your gross income, filing status, state, and age. The calculator computes your 2025 federal income tax using the IRS bracket tables, adds FICA (Social Security 6.2% up to $176,100, plus Medicare 1.45% on all earnings and an Additional 0.9% above $200K single / $250K MFJ), and adds state income tax. Then it sums the dollar value of maxing each tax-advantaged account based on your marginal rate.

What is the difference between HSA, 401(k), and Mega Backdoor Roth?

An HSA gives a triple tax benefit (deductible going in, tax-free growth, tax-free withdrawals for medical) but requires an HSA-eligible health plan. A traditional 401(k) is pre-tax going in, taxed coming out. The Mega Backdoor Roth uses your 401(k)’s after-tax bucket plus in-plan conversion or in-service withdrawal to put up to $70,000 (2025 limit) into a Roth account — only available if your employer’s plan supports it.

What is the SECURE 2.0 super catch-up?

Starting in 2025, workers aged 60, 61, 62, and 63 can contribute a larger catch-up to their 401(k) — the greater of $10,000 or 150% of the regular catch-up limit (indexed). Once you turn 64, you drop back to the standard catch-up. The calculator models this automatically based on your age.

Which states does this calculator use full bracket tables for?

CA, NY, NJ, OR, MN, MD, and HI use full bracket tables (and CA/HI include the additional millionaire surtax). Every other state uses its top marginal rate as a conservative estimate — overstating tax in low brackets and matching reality only at the top. For very precise state numbers in a non-listed state, consult a CPA.

Does this calculator handle the AMT or NIIT?

No — it focuses on regular federal income tax + FICA + state. Alternative Minimum Tax (AMT) rarely binds for W-2 earners under the post-TCJA exemption thresholds. Net Investment Income Tax (NIIT, 3.8%) applies to MAGI above $200K single / $250K MFJ on investment income only, not wages — out of scope for a wage-based contribution calculator.

Are these the maximum allowed contributions?

Yes — the calculator assumes you fully max each strategy that your income supports. For the Mega Backdoor Roth specifically, the practical max depends on your employer’s plan offerings and your salary level (after employer match and elective deferral). The calculator uses the total 415(c) limit ($70K in 2025) as the ceiling.

Calculator

Tax Savings Calculator

See what you'd save in 2025 by maxing your HSA, 401(k), Mega Backdoor Roth, and IRA — based on your income, filing status, and state.

2025 IRS limits · Federal + FICA + state · Updates live as you type

Your situation

Age

yrs

Affects 401(k) and IRA catch-up limits (50+, 60-63).

State

Local income tax (optional)

% / yr

e.g. NYC: 3.876%, Philadelphia: 3.75%, San Francisco: 0.

Annual W-2 income

Filing status

Single MFJ HoH

Children (for 529)

HDHP eligible? (for HSA)

Yes No Don't know

"Don't know" treated as No.

After-tax 401(k) at work?

Yes No Don't know

Required for Mega Backdoor Roth.

Your annual tax savings

If you max every applicable strategy

Marginal rate

Effective rate

Tax burden today

Before any tax-advantaged strategies. 2025 brackets, standard deduction, FICA, state.

Strategy-by-strategy savings

Each row: contribution amount × your marginal rate (federal + state + FICA where applicable).

If you do this every year, with 7% growth…

Annual tax savings reinvested at 7% nominal — what they compound to.

How the math works. Federal: 2025 brackets + standard deduction (Single $15,000 / MFJ $30,000 / HoH $22,500). FICA: SS 6.2% up to $176,100 wage base + Medicare 1.45% on all wages + Additional Medicare 0.9% above $200k single / $250k MFJ. State: top marginal rate per state — for incomes in lower state brackets, actual savings are slightly lower. HSA savings include FICA deduction (assuming employer-sponsored payroll deduction). Mega Backdoor Roth doesn't reduce current-year tax — instead, the figure shows estimated future capital gains tax avoided on tax-free Roth growth (assuming 30 years at 7%, 20% LTCG). 529 has no federal income tax deduction; state benefits vary widely and are not modeled here.

Sources: IRS Rev. Proc. 2024-40 (2025 inflation-adjusted limits), IRS Notice 2024-80 (retirement contribution limits), Tax Foundation 2025 state brackets. Educational estimate — not tax advice.