Roth 401k Calculator

A Roth 401(k) is a designated Roth account inside your employer's 401(k) plan. Your Roth contributions are taxed as pay in the year you make them, and qualified withdrawals, earnings included, are tax-free. Pre-tax (traditional) contributions work the other way round: they are left out of your taxable income now, and everything you take out later is taxed as income. A plan that offers Roth contributions must also offer pre-tax ones.

It puts the same yearly contribution into each kind of account and grows both at your return. The pre-tax side saves income tax every year and pays tax on everything it withdraws; the Roth side pays nothing later. To make the comparison fair, the pre-tax side can invest its yearly tax saving in a taxable account, whose growth is taxed once at the end.

The tax saved now is worked out exactly on the 2026 federal brackets: a pre-tax contribution comes off the top of your taxable income, so it saves tax at your highest rates first. With $55,000 of taxable income as a single filer, a $10,000 contribution is $4,600 at 22% and $5,400 at 12%, saving $1,660. For retirement you can enter a rate, or your expected taxable income in today's dollars; the calculator then uses the 2026 bracket rate on your last dollar. The IRS adjusts the brackets for inflation every year (Rev. Proc. 2025-32 set the 2026 figures), which is why retirement income is entered in today's dollars. Congress can change the rates themselves.

An example with the calculator's starting values: a single filer earning $90,000 with the $16,100 standard deduction has $73,900 of taxable income, so a $10,000 pre-tax contribution saves $2,200 a year at 22%. Over 30 years at 6%, either 401(k) grows to $838,017. With $50,000 of taxable income in retirement, the last dollar is taxed at 12%, so the pre-tax 401(k) is worth $737,455 after tax, plus $166,609 in the taxable account after a 15% tax on its growth: $904,064 against $838,017 for the Roth.

The break-even rate is the retirement tax rate at which both choices leave you with the same money. It equals the after-tax value of the taxable account divided by the 401(k) balance. If the taxable account paid no tax at all, it would equal your rate now: in the example, both come out at $838,017 when the retirement rate is also 22%.

Tax on the taxable account's growth lowers the break-even rate, because the Roth shelters all its growth while the pre-tax side's extra money does not. In the example it falls to 19.9%. At the same 22% rate in retirement as now, the Roth ends up $17,755 ahead. If you would spend the tax saving instead of investing it, the break-even rate is 0%: the Roth ends up $100,562 ahead in the example, but you would have had $66,000 more to spend along the way.

Your Social Security and Medicare tax is the same either way, because pre-tax 401(k) deferrals are still wages for those taxes (IRS Tax Topic 424).

From 2026, if your 2025 wages from the employer that sponsors your 401(k) were over $150,000, your catch-up contributions have to be Roth. Wages means wages for Social Security (FICA) tax from that employer, not your total income, so a partner's self-employment income does not count. At 55 you could put in $24,500 as pre-tax or Roth, and the other $8,000 only as Roth. The calculator applies this when you tick the box, and compares only the part you can choose.

Deferrals above the $24,500 limit are the catch-ups. The final regulations let Roth contributions you made earlier in the year count toward the Roth catch-up, and let a plan treat your catch-ups as Roth automatically once your deferrals pass the limit. If a plan has no Roth option, participants over the wage threshold cannot make catch-up contributions at all.

The IRS transition period generally ended on December 31, 2025. The final regulations (26 CFR 1.414(v)-2) generally apply from 2027, or later for certain governmental and collectively bargained plans; for 2026, plans can follow a reasonable, good faith reading of the law, so check how yours handles it.

An employer match normally goes into a pre-tax account, whether your own contributions are Roth or pre-tax. It is not taxed when it goes in, so it is not part of your cost in the plan, and it is taxed as income when you take it out, like the earnings on it (Publication 575). That is the same for both choices, so the calculator leaves it out.

Since the SECURE 2.0 Act (section 604), for contributions after December 29, 2022, a plan may let you designate matching or nonelective employer contributions as Roth. IRS Notice 2024-2 sets the rules:

• You can only designate employer money as Roth if you are fully vested in that type of contribution when it goes into your account.
• It is included in your income for the year it is allocated to your account. It is not wages for income tax withholding, so you may need to raise your withholding or pay estimated tax.
• In a 401(k) it is not wages for Social Security and Medicare tax, and the plan reports it on Form 1099-R.
• A plan does not have to offer every kind of Roth contribution: it can allow Roth deferrals without a Roth match, or the other way round.

The IRS FAQ page on designated Roth accounts still says a match must go into a pre-tax account. That answer predates the change; the amended law (26 U.S.C. 402A(a)(2) and (3)), Notice 2024-2 and Publication 575 (2025) allow Roth employer contributions where the plan offers them.

A qualified distribution from a Roth 401(k) is not taxed at all. It has to meet both tests:

• The 5-taxable-year period: it starts on the first day of the first tax year for which you made Roth contributions to that plan and ends after five full years. Publication 575's example: a first contribution for 2025 allows qualified distributions from 2030; a first contribution for 2026 means 2031. A direct rollover from another plan's Roth account can bring its earlier start date with it.
• A qualifying reason: you are 59½ or older, you are disabled, or it is paid after your death. Unlike a Roth IRA, a first home purchase does not count.

A withdrawal that is not qualified is split in proportion between your contributions, which are not taxed, and earnings, which are. The IRS example: $5,000 taken from an account holding $9,400 of contributions and $600 of earnings is $4,700 of contributions and $300 of taxable earnings. Before 59½ the taxable part can also owe the 10% additional tax unless an exception applies; see the 401(k) early withdrawal calculator. Roth money is also no easier to reach: the plan's rules on when you can withdraw apply to Roth and pre-tax money alike.

Roth 401(k) money can be rolled over only to another plan's Roth account (by direct rollover) or to a Roth IRA. A plan may also let you convert pre-tax money to Roth inside the plan, an in-plan Roth rollover; the taxable amount counts as income that year but does not owe the 10% additional tax, unless you take that money out within five years and no exception applies. The Roth conversion calculator shows the federal tax on a conversion.

From 2024, Roth 401(k) accounts have no required minimum distributions while you are alive (26 U.S.C. 402A(d)(5), added by SECURE 2.0 section 325). Pre-tax 401(k) money still has them, generally from the year you reach 73, or from retirement if later and your plan allows the delay. People who inherit a Roth 401(k) are still subject to the RMD rules. The RMD calculator works out the pre-tax amount.