Roth vs traditional 401(k) calculator

Same take-home cost, two tax deals. See which one leaves you more to spend in retirement, and by how much.

In short: A Roth 401(k) beats a traditional 401(k) when your tax rate in retirement will be higher than today; traditional wins when it will be lower; they tie when the rates are equal, for the same take-home cost.

Traditional comes out ahead by $39,185

After tax, the traditional 401(k) leaves $475,814 and the Roth $436,630 after 30 years, in today's dollars.

Traditional, after tax: $475,814
Roth, after tax: $436,630
Retirement tax rate where they tie: 22%

What would change your result

If your retirement tax rate turns out to be 32%, Roth wins by $55,978.
Not sure about future tax rates? Splitting 50/50 lands at about $456,222, between the two outcomes.
Contributing $2,000 more a year adds about $95,163 after tax, more than the choice of account.

What-ifs worked out from your own numbers. Not personal financial advice.

Roth, after tax
Traditional, after tax

Using a 3.88% real return. All amounts in today's dollars. Both cost you the same take-home pay each year.

Year-by-year table

Year	Roth, after tax	Traditional, after tax
0	$0	$0
1	$7,938	$8,650
2	$16,184	$17,636
3	$24,750	$26,972
4	$33,649	$36,669
5	$42,894	$46,744
6	$52,498	$57,209
7	$62,474	$68,081
8	$72,839	$79,375
9	$83,605	$91,108
10	$94,790	$103,297
11	$106,409	$115,958
12	$118,479	$129,112
13	$131,018	$142,776
14	$144,044	$156,971
15	$157,576	$171,717
16	$171,633	$187,036
17	$186,236	$202,950
18	$201,407	$219,482
19	$217,166	$236,656
20	$233,538	$254,496
21	$250,545	$273,030
22	$268,213	$292,283
23	$286,567	$312,284
24	$305,633	$333,062
25	$325,441	$354,647
26	$346,017	$377,070
27	$367,392	$400,364
28	$389,598	$424,562
29	$412,666	$449,700
30	$436,630	$475,814

A worked example

With these inputs:

Yearly contribution$10,000
Tax rate today22%
Tax rate in retirement15%
Years until retirement30 years
Expected return7%
Inflation3%

the calculator returns Traditional comes out ahead by $39,185. After tax, the traditional 401(k) leaves $475,814 and the Roth $436,630 after 30 years, in today's dollars.

Its first suggestion: If your retirement tax rate turns out to be 32%, Roth wins by $55,978.

Key facts

Traditional contributions are pre-tax and withdrawals are taxed as ordinary income; Roth contributions are after-tax and qualified withdrawals are tax-free.
Since 2024 Roth 401(k)s have no required minimum distributions for the original owner.
There is no income limit on Roth 401(k) contributions, unlike a Roth IRA.

How it's calculated

For a fair comparison both options cost the same take-home pay. A traditional contribution of $10,000 is pre-tax; the Roth equivalent is $10,000 × (1 − tax rate today), because you pay the tax first.

Both grow at the same real return. At retirement the traditional balance is taxed at your retirement rate; the Roth is tax-free. The result: Roth wins when your tax rate later is higher than today, traditional wins when it is lower, and they tie when it is the same.

Not included: the employer match (it goes in either way), state tax changes if you move, and Roth's other perks such as no required distributions. Read more in our Roth vs traditional guide.

Questions people ask

Is a Roth 401(k) better than a traditional 401(k)?

It depends on your tax rate now versus in retirement. Roth wins if it will be higher later; traditional wins if it will be lower.

What tax rate should I use for retirement?

Think about the income you will have: withdrawals from traditional accounts, part of your Social Security, pensions. Many retirees with modest income land in the 10% to 12% federal brackets.

Can I split between Roth and traditional?

Yes. Most plans let you choose a percentage for each. Splitting hedges against not knowing future tax rates.

Does my employer match go into the Roth?

Usually it goes into the pre-tax side. Some plans now allow a Roth match under SECURE 2.0, taxed as income that year.