How to use this Roth 401(k) calculator
- Choose your filing status and enter your salary before tax.
- Enter what you put into your 401(k) each year and your age band, which sets the 2026 limit including catch-up contributions.
- Enter the years until you retire.
- Under "In retirement", either enter the yearly income you'll need before tax plus your taxable income from other sources, or type the tax rate you expect on 401(k) withdrawals.
- Open Assumptions to change the return, inflation or the tax rate on gains in a taxable account.
Results update as you type. The share link saves your scenario, and the CSV has the after-tax value of both at every tax rate.
How does the calculator compare Roth and traditional?
It compares the two at equal take-home pay. Traditional (pre-tax) contributions are left out of your taxable wages[4], so they lower this year's income tax. Roth contributions are taxed now, and qualified withdrawals later, after a 5-year period and age 59½, are tax-free[5].
Put the same amount in either way and the traditional saver keeps more pay this year. Ignoring that money would tilt the result toward Roth, so the calculator assumes the traditional saver invests the tax saving every year in a taxable brokerage account. At retirement:
- Roth after tax = 401(k) balance
- Traditional after tax = 401(k) balance × (1 − retirement tax rate) + taxable account after tax on its gains
- Break-even rate = taxable account after tax ÷ 401(k) balance
If the taxable account paid no tax, the break-even rate would equal today's rate on your contribution, the familiar rule of comparing your tax rate now with your rate later. In the first example below that is 22%. Tax on the account's gains pulls the break-even down to 19.9%, which tilts the choice slightly toward Roth.
Today's rate is measured with the brackets, not guessed: it's the federal tax with and without the contribution, divided by the contribution. If you choose to enter the income you'll need, the retirement rate is the average 2026 federal rate on the slice of income your 401(k) withdrawals add above your other income, after the standard deduction. Everything is in today's dollars. The IRS adjusts the brackets for inflation each year (Rev. Proc. 2025-32 sets the 2026 figures[1]), and the calculator assumes that continues.
Worked example: Roth or traditional on a $90,000 salary?
Alex is single, earns $90,000 and puts $10,000 a year into the 401(k) for 30 years. In retirement Alex expects to need $60,000 a year before tax, $24,000 of it from a pension and part-time work. Returns are 7% with 3% inflation, and gains in the taxable account are taxed at 15%.
- Tax saved by contributing pre-tax this year: $2,200, a rate of 22% (Alex is in the 22% bracket)
- 401(k) balance at retirement either way: $550,058 in today's dollars
- Retirement rate on the $36,000 a year of 401(k) withdrawals: 11.8%
- Roth after tax: $550,058. Traditional after tax: $485,426 plus $109,523 from the invested tax savings = $594,949
- Break-even retirement rate: 19.9%
Alex's expected 11.8% is below 19.9%, so traditional comes out about $44,891 ahead. The standard deduction and the 10% and 12% brackets make the first dollars of retirement income cheap, while Alex's contributions today come off the top of the 22% bracket.
When does a Roth 401(k) come out ahead?
When today's rate is low and retirement income will be high. Jordan is 25, single, earns $55,000 and saves $6,000 a year for 40 years, aiming for $90,000 of yearly income in retirement with $30,000 from other sources.
- Today's rate on the contribution: 12%. Break-even: 10.7%
- Retirement rate on $60,000 a year of withdrawals: 15.9%
- Roth after tax: $554,736 vs traditional $525,595
Roth leaves about $29,141 more, because Jordan's retirement income would reach the 22% bracket while the contributions only save 12% now. A pay rise later in Jordan's career can flip the answer, so it's worth checking again as income grows.
Filing status matters too. The single brackets are half as wide as the joint ones up to the 32% bracket (the 22% rate starts above $50,400 single and $100,800 joint)[1], so a surviving spouse who later files as single on similar income would pay higher rates.
Should high earners choose traditional?
Often, yes. Sam and Riley file jointly, earn $300,000 and put in the full $24,500 for 25 years. They plan on $160,000 a year in retirement, $50,000 of it from other income.
- Today's rate on the contribution: 24% (24% bracket), saving $5,880 a year
- Retirement rate: 14.3%, against a break-even of 22%
- Traditional after tax: $1,081,279 vs Roth $1,004,462
At the contribution limit, Roth has one quiet advantage: the same $24,500 buys more after-tax money, because the tax is paid from outside the account. The calculator captures it, since the traditional saver's extra savings sit in a taxable account that owes tax on its gains. Here the gap between 24% today and 14.3% in retirement decides it: traditional leaves about $76,817 more.
What are the 2026 federal tax brackets?
The calculator uses the 2026 ordinary income tax brackets and standard deduction ($16,100 single, $32,200 married filing jointly) from IRS Rev. Proc. 2025-32[1][2]. The ranges are taxable income, after the deduction.
| Rate | Single | Married filing jointly |
|---|---|---|
| 10% | $0 to $12,400 | $0 to $24,800 |
| 12% | $12,400 to $50,400 | $24,800 to $100,800 |
| 22% | $50,400 to $105,700 | $100,800 to $211,400 |
| 24% | $105,700 to $201,775 | $211,400 to $403,550 |
| 32% | $201,775 to $256,225 | $403,550 to $512,450 |
| 35% | $256,225 to $640,600 | $512,450 to $768,700 |
| 37% | Over $640,600 | Over $768,700 |
Source: IRS Rev. Proc. 2025-32, section 4.01. Each rate applies only to the income inside its range.
What are the 2026 401(k) contribution limits?
You can defer up to $24,500 in 2026. From age 50 you can add a catch-up contribution of $8,000, and at ages 60 to 63 the catch-up is $11,250 instead, for a total of $35,750[3]. Roth and pre-tax contributions share that one limit, and you can split it between them however you like[5]. To project your whole balance with an employer match, use the 401(k) calculator.
What does this calculator leave out?
- State and local income tax. Moving from a high-tax state to one with no income tax favors traditional; the reverse favors Roth.
- Payroll tax. Both choices pay the same Social Security and Medicare tax, because pre-tax deferrals still count as wages for them[4].
- Other parts of the tax return. Tax on Social Security benefits, the extra standard deduction from 65, the net investment income tax, credits and itemized deductions.
- The yearly tax on dividends in the taxable account. It would make traditional look slightly worse than shown.
- Early withdrawals. Pre-tax money taken before 59½ usually owes an extra 10% unless an exception applies[8], and Roth earnings are only tax-free in a qualified distribution.
- Changes in tax law. The comparison assumes 2026 rules for the rest of your life. Nobody knows future rates, which is one reason to hedge.
Why do many people split between Roth and traditional?
Because the answer depends on a tax rate decades away. Holding both gives you a choice each year in retirement: draw pre-tax money to fill the low brackets, then use Roth money for the rest. Roth 401(k)s also skip required minimum distributions while you're alive, while pre-tax accounts generally must start them at 73[7].
Early retirees have another option. The low-income years between leaving work and claiming Social Security are a chance to convert pre-tax money to Roth at low rates, and each conversion has its own 5-year period before it can be withdrawn freely[9]. The early retirement calculator shows how to bridge those years.
This calculator compares the two choices under the assumptions you enter. It isn't tax advice; for a decision with large sums, a tax professional can check your whole return.