Roth or traditional: which leaves you more after tax?
A traditional contribution cuts your tax bill now and is taxed when you withdraw it. A Roth contribution is taxed now and can come out tax-free later. The comparison mostly comes down to two rates: the one this contribution saves today and the one your withdrawals pay in retirement.
Pay the tax now, or later?
Compare one year of Roth and traditional contributions at the same take-home cost, using 2026 federal brackets for the tax you save now and the tax you pay on withdrawals.
The example, step by step.
The situation
- A single filer with $120,000 of 2026 taxable income
- A $10,000 traditional 401(k) contribution, or a Roth contribution with the same take-home cost
- 30 years of growth at 5% a year after inflation
- $60,000 of other taxable income in retirement, with withdrawals spread over 20 years
What the calculator finds
- The traditional contribution saves $2,400 of federal tax now (24%), so the same take-home cost buys a $7,600 Roth contribution.
- Traditional grows to $43,219 and supports $3,468 a year of withdrawals. Taxed at 22%, that leaves $2,705 a year.
- Roth grows to $32,847 and supports $2,636 a year, tax-free.
- Under these assumptions traditional comes out about $69 a year ahead. The break-even retirement rate is 24%: below it traditional leaves more, above it Roth does.
The comparison turns on two rates: what the contribution saves you today and what the withdrawals cost you later. When they are equal, the two choices leave the same after-tax income.
What goes in.
What comes out.
Enter your filing status, your 2026 taxable income before the contribution, and the amount. The calculator uses 2026 federal brackets to find the tax the traditional contribution saves now.
To compare like with like, the Roth contribution is the traditional amount minus that tax saving, so both cost the same take-home pay today.
Both grow at the same return after inflation. Traditional withdrawals are then taxed on top of your other retirement income using today’s brackets, which are assumed to rise with inflation. You can add flat state rates for now and for retirement.
What it does not cover.
- One year’s contribution, not your whole retirement plan.
- It assumes the contribution is allowed and, for a traditional IRA, fully deductible. It does not test Roth IRA income limits or IRA deduction limits.
- Required minimum distributions, taxation of Social Security benefits, Medicare premium surcharges (IRMAA), employer matches and future changes in tax law are not modeled.
Questions
Is a Roth or a traditional contribution better?
Neither is better in general. If the tax rate on your future withdrawals is lower than the rate a contribution saves today, traditional tends to leave more after tax. If it is higher, Roth does. At the same rate they come out about even at the same take-home cost.
Why is the Roth amount smaller in the comparison?
A $10,000 traditional contribution only costs $7,600 of take-home pay when it saves $2,400 of tax. Comparing it with a $7,600 Roth contribution keeps the cost the same, so the difference you see comes from the tax rates, not from saving more.
Does it include state income tax?
Only if you enter it. You can add one flat state rate for now and another for retirement, for example if you expect to move.
Which tax brackets does it use?
The 2026 federal ordinary income brackets for single and married-filing-jointly filers. Retirement brackets are assumed to keep pace with inflation, so retirement amounts are in today’s dollars.
See the decision inside a full plan.
Explore retirement cash flow, compare scenarios and review the assumptions in a free Amicus sample plan.