Pay tax now or later?
Roth and Traditional grow the same money differently — Roth is taxed on the way in, Traditional is taxed on the way out. Which wins depends on whether your tax bracket is higher today or in retirement. Punch in the numbers and see.
Estimates only. Same-out-of-pocket comparison: Roth contributes the input amount as after-tax dollars; Traditional contributes the gross-of-tax equivalent. Real life adds the IRS contribution cap, RMDs, state tax, and unknowable future bracket changes. Plan documents and a CPA beat any calculator.
What it looks like to max out a Roth IRA.
The 2026 IRA contribution limit is $7,500/yr (under 50) — about $625/mo. At an 8% annualized return, here's where each level of monthly contribution lands you over five common time horizons.
| Monthly | After 5 yrs | After 10 yrs | After 20 yrs | After 30 yrs | After 40 yrs |
|---|---|---|---|---|---|
| $10 | $735 | $1,829 | $5,890 | $14,904 | $34,910 |
| $25 | $1,837 | $4,574 | $14,726 | $37,259 | $87,275 |
| $50 | $3,674 | $9,147 | $29,451 | $74,518 | $174,550 |
| $100 | $7,348 | $18,295 | $58,902 | $149,036 | $349,101 |
| $250 | $18,369 | $45,737 | $147,255 | $372,590 | $872,752 |
| $375 | $27,554 | $68,605 | $220,883 | $558,885 | $1,309,128 |
| $625 2026 max · $7,500/yr | $45,923 | $114,341 | $368,138 | $931,475 | $2,181,880 |
Assumes monthly contributions, 8% annualized return, monthly compounding, no fees or taxes. The 2026 IRA limit applies to your combined Traditional + Roth IRA contributions; the under-50 cap is $7,500 ($625/mo).
The bracket gap is the whole game.
When tax brackets are equal now and later, Roth and Traditional are mathematically identical — same growth, same after-tax outcome. The difference only shows up when brackets change. Pay tax at the lower of the two rates and you win.
Roth = lock in today's tax rate. Traditional = bet that retirement will be a lower-tax year. The math doesn't care which you pick if the brackets end up equal.
What this calculator actually compares.
The trick to a fair Roth-vs-Traditional comparison is keeping your
out-of-pocket cost equal. Putting $6,000 of post-tax
paycheck into a Roth costs you the same paycheck cash as putting
$6,000 / (1 − bracket) pre-tax into a Traditional —
because the Traditional contribution would have been taxed before
you saw it.
- Roth. You contribute the input amount as after-tax dollars. It grows tax-free; withdrawals in retirement are tax-free. Net = full balance.
- Traditional. You contribute the gross-of-tax equivalent (more dollars) pre-tax. It grows tax-deferred; withdrawals in retirement are taxed at your future bracket. Net = balance × (1 − retirement bracket).
- Why same out-of-pocket? If you compared raw contribution dollars ($6,000 in either), Traditional would look worse than it is — you'd be ignoring the tax it saves you today.
Where this estimate is rough.
- Bracket prediction is hard. You don't actually know your retirement bracket. If you're early-career and earning entry-level wages, lean Roth — your bracket is probably as low as it'll ever be.
- Contribution caps differ in practice. The IRS limit is the same dollar amount for both — but if you can max out, Roth lets you shelter more after-tax money than Traditional. That's a real edge.
- RMDs and conversions. Traditional accounts have required minimum distributions starting at 73; Roth IRAs don't. That changes the late-retirement math.
- State tax matters. If you live in a high-state-tax state now and plan to retire in a no-state-tax state, Traditional gets a quiet bonus.
- Tax law changes. Rates, brackets, and rules have changed every decade for a century. The calculator assumes today's rate ≠ tomorrow's, but neither input is set in stone.