Meet the 401(k) / IRA Optimizer: The $100K Question You've Been Avoiding

The Traditional vs. Roth decision is one of the most consequential choices you'll make — and one of the most misunderstood. "Roth is always better because it grows tax-free" is wrong. "Traditional is always better because of the upfront deduction" is also wrong. The real answer is math, and it depends on your specific numbers.

Alistair's 401(k) / IRA Optimizer Microtool runs through your tax bracket, employer match, contribution rate, age, and current balance to find your optimal split.

What the Tool Calculates

The optimizer takes six inputs and produces a recommendation grounded in tax bracket analysis, not conventional wisdom:

Tax Bracket Arbitrage

The core idea: if your tax rate is higher today than it will be in retirement, Traditional wins. If it's lower today, Roth wins. If they're roughly equal, it's a wash.

But that's the simplified version. The tool accounts for:

• Progressive tax brackets in retirement: You don't withdraw everything at your top marginal rate. Some comes out at 0% (standard deduction), some at 10%, some at 12%, and so on. This makes Traditional more attractive than a simple bracket comparison suggests.

• Employer match: This is free money that always goes in pre-tax. Your match effectively tilts your overall allocation toward Traditional, which may mean you should lean Roth on your own contributions for tax diversification.

• RMD considerations: Traditional accounts force withdrawals starting at age 75. Roth accounts don't. If you're a high saver, RMDs could push you into a higher bracket in retirement — making Roth more attractive.

• Current vs. future balance: The tool projects your balance at retirement age under both strategies, showing you the total account value and the after-tax value (since $1 in Traditional is worth less than $1 in Roth).

Contribution Optimization

Beyond the Traditional/Roth split, the tool shows you:

• How much you're leaving on the table below the annual contribution limit
• The dollar value of your employer match (and whether you're capturing all of it)
• Catch-up contribution eligibility (age 50+) and how it changes the math

Real Numbers: A 35-Year-Old in the 24% Bracket

• Income: $120,000 (24% federal marginal rate)
• Employer match: 50% of first 6% (effectively 3%)
• Current contribution: 10% ($12,000/year)
• Current balance: $50,000
• Age: 35
• Expected return: 7%

The tool's analysis:

First, the match: contributing 10% captures the full match (the match caps at 6%). That's $3,600/year in free money — non-negotiable, always get the full match.

For the contribution split: at 24% today, the tool examines what retirement tax bracket this saver is likely to land in. Their Traditional balance at 65 projects to roughly $680,000 (in today's dollars, accounting for inflation). A 4% withdrawal is $27,200/year. In today's tax brackets, that's mostly in the 12% bracket.

Conclusion: Traditional contributions are strongly favored. The 24% deduction today is more valuable than the 12% tax rate on withdrawals in retirement. The tool recommends a 70/30 Traditional/Roth split to maintain some tax diversification.

If the same person were in the 12% bracket today, the recommendation flips: Roth becomes the clear winner, because the 12% "cost" of going Roth is negligible compared to the tax diversification benefit.

Why Most People Get This Wrong

Financial advisors often default to "max out your Traditional 401(k)" because it's simpler and they don't want to explain bracket math. Online calculators ask for your "expected retirement tax rate" — a number nobody actually knows. And generic advice like "Roth is better when you're young" ignores the fact that young people in the 22% bracket might benefit more from Traditional deductions.

Alistair doesn't guess. It runs your numbers against today's tax brackets, projects your retirement income, and gives you a data-backed split.

That's what this microtool does. Stop guessing on the biggest account in your portfolio.