What it does
A traditional 401(k) or IRA saves tax now and is taxed when you take money out. A Roth is taxed now and comes out tax-free. Which leaves you more depends mostly on one thing: is your tax rate higher now or in retirement? This calculator grows your yearly contributions both ways and shows the after-tax value of each, the tax rate at which they tie, and a table for a range of retirement tax rates. It also shows your 2026 contribution limit.
Work out today’s tax rate from your pay with the US paycheck calculator, plan the whole retirement with the retirement planner, or compare Canada’s version of the same choice in RRSP or TFSA.
How to use it
- Pick the account and your age (this sets your limit and catch-up).
- Type what you put in each year before tax, the years until you retire and a yearly return.
- Type your tax rate now (your top federal plus state rate) and your expected tax rate in retirement.
- Choose how to compare.
What each option does
- Same cost to my take-home pay: $1 in a traditional costs you the same as $1 minus tax in a Roth. This is the fair test below the limit.
- Same dollars into the account: for when you put in the full limit either way. The traditional’s tax saving is invested in a normal account, whose returns are taxed each year at the rate you type.
- Break-even tax rate later: if your retirement rate is lower than this, traditional wins; higher, Roth wins.
Worked example
Maria puts $6,000 a year into her 401(k) for 30 years at 6%. Her tax rate is 22% now and she expects 12% in retirement. The traditional pot grows to $502,810; after 12% tax she keeps $442,473. The Roth version costs the same take-home pay, so $4,680 goes in each year and grows to $392,192, tax-free. Traditional wins by $50,281. With the same 22% rate later, they tie exactly.
FAQs
What about my employer’s match? Matches go in pre-tax, whichever you choose, so they do not change the comparison.
Should I split between both? Many people do, because nobody knows future tax rates. The table shows how much is at stake either way.
Is anything saved? No. Nothing you type leaves the page. Not financial or tax advice; check the official source.
Where the numbers come from
- 2026 limits: 401(k) $24,500, catch-up $8,000 (50+) and $11,250 (60-63); IRA $7,500, catch-up $1,100; Roth IRA phase-out $153,000-$168,000 single and $242,000-$252,000 joint: IRS IR-2025-111, https://www.irs.gov/newsroom/401k-limit-increases-to-24500-for-2026-ira-limit-increases-to-7500 (checked 2026-11-10)
- Method: compound growth of yearly contributions; traditional withdrawals taxed at the retirement rate, Roth withdrawals tax-free (qualified). fibub's own calculation.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.