What is a roth 401(k) vs Traditional 401(k) calculator?

A roth 401(k) vs Traditional 401(k) calculator is a free online tool that helps you same analysis applied to 401(k) Roth vs Traditional elections. Same math as Roth vs Traditional IRA. It runs entirely in your browser with instant results and no sign-up.

What withdrawal rate is safe?

The Trinity Study's 4% rule (4% of starting portfolio, adjusted for inflation each year) gave a >95% success rate for 30 years in historical US data. Recent research (Pfau 2020) suggests 3-3.5% may be safer for early retirees or longer horizons.

When should I claim Social Security?

Each year you delay past FRA boosts your benefit ~8% (up to age 70). Each year you claim early reduces it ~5-6%. Break-even is typically age 80-82, so if you expect to live past that, delaying usually wins.

Are these guaranteed?

No — projections assume average returns. Real markets have sequence-of-returns risk. Use these for planning; expect a wide range of actual outcomes.

Free roth 401(k) vs traditional 401(k) calculator

How it's calculated

How the roth 401(k) vs traditional 401(k) works

Same math as Roth vs Traditional IRA.

compare after-tax FV both ways

Source: standard retirement planning formulas. Tax rules per IRS Pub 590, 575, 939.

Accuracy

How accurate is this roth 401(k) vs traditional 401(k)?

Every formula on this site comes from an established, published source for its field — standard references in mathematics, finance, health, and engineering, not invented in-house. The math is implemented as a pure TypeScript function and tested against published reference values before going live. See the Methodology page for the full sourcing process.

Results are mathematically correct for the inputs provided. They are estimates only— real-world outcomes depend on factors specific to your situation, such as fees, taxes, timing, local rules, and assumptions that can change after the calculation date. See the Disclaimer for the limits on what to rely on a result for.

These pair naturally with this one for decisions that sit nearby.

Questions

Frequently asked questions about the free roth 401(k) vs traditional 401(k) calculator

What is a roth 401(k) vs Traditional 401(k) calculator?
A roth 401(k) vs Traditional 401(k) calculator is a free online tool that helps you same analysis applied to 401(k) Roth vs Traditional elections. Same math as Roth vs Traditional IRA. It runs entirely in your browser with instant results and no sign-up.
What withdrawal rate is safe?
The Trinity Study's 4% rule (4% of starting portfolio, adjusted for inflation each year) gave a >95% success rate for 30 years in historical US data. Recent research (Pfau 2020) suggests 3-3.5% may be safer for early retirees or longer horizons.
When should I claim Social Security?
Each year you delay past FRA boosts your benefit ~8% (up to age 70). Each year you claim early reduces it ~5-6%. Break-even is typically age 80-82, so if you expect to live past that, delaying usually wins.
Are these guaranteed?
No — projections assume average returns. Real markets have sequence-of-returns risk. Use these for planning; expect a wide range of actual outcomes.