Roth 401(k) Calculator: Project Tax-Free Retirement Growth
Project how a Roth 401(k) could grow when funded with after-tax pay, so that qualified withdrawals in retirement are entirely tax-free.
Adjust the inputs and select Calculate for a full breakdown.
Year-by-year growth schedule
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Future value | Total contributions | Total interest earned |
|---|---|---|---|
| $25k · $700/mo · 7% · 30yr | $1,056,892.13 | $277,000.00 | $779,892.13 |
| $0 · $500/mo · 8% · 35yr | $1,146,941.24 | $210,000.00 | $936,941.24 |
| $120k · $1k/mo · 6% · 20yr | $859,265.43 | $360,000.00 | $499,265.43 |
| $60k · $900/mo · 7% · 25yr | $1,072,589.62 | $330,000.00 | $742,589.62 |
How This Calculator Works
Enter the current Roth 401(k) balance, the average annual return you expect, the years until retirement, and your monthly contribution. The calculator compounds the balance monthly and adds each contribution, showing the projected balance and the growth.
The Formula
Future Value with Regular Contributions
P = starting amount, PMT = monthly contribution, r = monthly rate (annual ÷ 12), n = number of months
Worked Example
With $25,000 saved, $700 added monthly, and a 7% average return over 30 years, a Roth 401(k) reaches about $1,056,900. Contributions account for $277,000; the rest is tax-free investment growth.
Key Insight
A Roth 401(k) combines a high contribution limit with tax-free qualified withdrawals. One wrinkle: an employer match is usually placed in a pre-tax account, so part of the total may still be taxed in retirement.
Frequently Asked Questions
How is a Roth 401(k) taxed?
Contributions are made with after-tax pay, and qualified withdrawals — including all growth — are tax-free once the account is five years old and you are 59½ or older.
How does it differ from a traditional 401(k)?
A traditional 401(k) is funded pre-tax and taxed on withdrawal; a Roth 401(k) is funded after-tax and withdrawn tax-free. The Roth wins if your retirement tax rate is similar or higher.
Is the employer match also tax-free?
Usually not. Employer matching contributions typically go into a pre-tax account, so that portion and its growth are taxed as income when withdrawn.
How does a Roth 401(k) compare with a Roth IRA?
Both offer tax-free qualified withdrawals, but a Roth 401(k) has a much higher contribution limit and no income cap, while a Roth IRA offers wider investment choice.
Is there a contribution limit?
Yes. The IRS sets an annual 401(k) contribution limit, with a higher cap for savers age 50 and older. Keep contributions within that limit.
Related Calculators
Data Sources & Benchmarks
This calculator draws on 3 independent, dated sources. The starting values for expected annual return are taken from the benchmarks below and refresh whenever the snapshots are updated.
Methodology & Review
The projection compounds the balance monthly at a constant expected return and adds a fixed monthly contribution. It assumes contributions stay within the annual 401(k) limit and excludes fees.
Written by Ugo Candido · Last updated May 17, 2026.