Roth vs Traditional calculator
The entire Roth-versus-Traditional question compresses into one comparison: your tax rate now versus your tax rate in retirement. This calculator makes that visible - same contributions, same growth, different tax timing - so you can see how the outcome shifts as the two rates change.
The honest caveat
Nobody knows future tax law, and most people’s income (and therefore rate) moves over a career. That uncertainty is why splitting contributions between both account types is such a common middle path - it diversifies the tax bet the same way index funds diversify the stock bet.
Related reading
Roth vs Traditional IRA walks the concepts, why people say Roth suits younger workers examines the age rule of thumb, and is it a big deal if you pick the wrong one puts the stakes in perspective. Starting from zero? See how to set up a 401k at your first job.
The formula this calculator uses
future value = contribution grown at the rate for the number of years
roth after tax = future value, taxed once on the way in
traditional after tax = future value * (1 - tax rate in retirement)
the two are equal when the rate today equals the rate in retirement
What it assumes without asking
- One flat tax rate today and one in retirement, which is a simplification of a bracket system
- A steady return with no fees
- Contributions inside the annual limit, and eligibility to make them
One example, computed in full: $6,000 of pre-tax income, 25 years at 7%
| Rate today | Rate in retirement | Roth after tax | Traditional after tax | Difference |
|---|---|---|---|---|
| 22% | 22% | $25,400.38 | $25,400.38 | tie |
| 12% | 22% | $28,656.84 | $25,400.38 | $3,256.46 to the Roth |
| 22% | 12% | $25,400.38 | $28,656.84 | $3,256.46 to the traditional |
| 24% | 32% | $24,749.09 | $22,143.93 | $2,605.17 to the Roth |
| 32% | 24% | $22,143.93 | $24,749.09 | $2,605.17 to the traditional |
What this calculator does not model
- Income phase-outs on Roth contributions and deduction limits on traditional ones
- State tax, which can point the other way from federal
- Any change in tax law over the holding period, which is the real uncertainty
- Required minimum distributions, which apply differently by account type
The guide behind this tool
A number on its own does not tell you what to do with it. Roth against traditional carries the full 6x6 grid of every pair of rates, which shows that the diagonal ties and the choice is a bet on your future bracket rather than on the account.
Sources & further reading
This tool is general education, not personalized financial or tax advice. It simplifies contribution limits, matches, and state taxes. See our disclaimer.