401(k): Pre-tax vs Roth
Pre-tax vs Roth 401(k) modeling with retirement taxes included
Compare traditional and Roth 401(k) contributions with explicit retirement-tax assumptions, sidecar investing, and RMD treatment.
The right answer on pre-tax versus Roth depends on lifetime tax structure, not current versus future brackets alone.
What the model includes
- Traditional and Roth employee deferrals.
- A taxable sidecar for current-year tax savings.
- Retirement taxes, Social Security taxation, and RMD treatment.
Why generic advice falls short
A traditional-versus-Roth decision changes once you include match treatment, state taxes, Social Security interactions, and the fact that you can invest pretax tax savings elsewhere.
What to focus on
- Current marginal rate versus retirement income mix.
- Employer match structure and contribution limits.
- Whether the model should run in real or nominal dollars.
What to read alongside it
- Tax Rates 2026 for bracket context.
- Compensation Planner when equity comp is part of the plan.
- The full docs for modeling notes and caveats.
FAQ
- Does the tool assume the Roth path has no employer match?
- No. The tool models employer match as pretax dollars in both paths. That detail matters when you compare after-tax outcomes later in retirement.