How this page is reviewed
| Risk tier | High YMYL |
|---|---|
| Author | Calculover Editorial Team Finance and legal education |
| Editorial owner | Calculover Tax & Payroll Desk Tax and wage methodology owner |
| Reviewer | Calculover Editorial Review High-risk source and limitation review |
| Last reviewed | 2026-05-10 |
| Last verified | 2026-05-10 |
| Data effective date | 2026-01-01 |
Methodology
401(k) vs Roth 401(k): Pre-Tax or After-Tax Contributions? applies the tax-rate, threshold, and taxable-base logic documented in the calculator formula section, then separates user-entered assumptions from statutory or source-linked rate inputs.
Assumptions
- 401(k) vs Roth 401(k): Pre-Tax or After-Tax Contributions? relies on the values the user enters and does not independently verify income, balances, legal status, policy terms, or market quotes.
- Taxable income, deductions, credits, filing status, jurisdiction, and timing are simplified to the fields available in the calculator.
- Federal, state, local, and international tax rules can change after the listed last-verified date.
Limitations
- 401(k) vs Roth 401(k): Pre-Tax or After-Tax Contributions? does not prepare a tax return, determine final liability, apply every credit or deduction, or account for all state, local, foreign, penalty, or surtax rules.
- Confirm current forms, thresholds, and filing obligations with the IRS, the relevant tax authority, or a qualified tax professional before filing or paying tax.
Sources
- Federal Income Tax Rates and Brackets, Internal Revenue Service
- Estimated Taxes, Internal Revenue Service
Professional guidance: 401(k) vs Roth 401(k): Pre-Tax or After-Tax Contributions? is for tax education and planning only and is not tax, legal, accounting, or filing advice. Verify current rules with the relevant tax authority or a qualified tax professional.
What Is a Traditional 401(k)?
A traditional 401(k) accepts pre-tax contributions, meaning your taxable income is reduced in the year you contribute. If you earn $80,000 and contribute $10,000, you're only taxed on $70,000. Your money grows tax-deferred, and you pay ordinary income tax when you withdraw in retirement.
The 2025 contribution limit is $23,500 ($31,000 if age 50+). Required minimum distributions (RMDs) begin at age 73. There are no income limits to participate if your employer offers the plan.
What Is a Roth 401(k)?
A Roth 401(k) accepts after-tax contributions — you pay taxes on the money before it goes in, but qualified withdrawals in retirement are completely tax-free. The same $23,500/$31,000 limits apply. Unlike a Roth IRA, there are no income limits for Roth 401(k) contributions.
Starting in 2024, Roth 401(k)s no longer require RMDs during the owner's lifetime (thanks to SECURE 2.0 Act), aligning them with Roth IRA rules.
Real-World Example
Many financial advisors recommend splitting contributions — for example, 60% traditional / 40% Roth — to create tax diversification. In retirement, you can withdraw from traditional in low-income years (filling up the 12% bracket) and from Roth in high-income years (avoiding bracket creep).
Someone contributing $23,500 total: $14,100 traditional + $9,400 Roth. The traditional portion saves ~$3,102 in taxes this year (22% bracket). The Roth portion grows tax-free for 30 years.