Free Calculator

Roth vs. Traditional TSP

See which contribution type leaves you with more after taxes in retirement — based on your tax rate today versus the rate you expect later. Private by design: every calculation happens on your device.

🔒 Everything is calculated on your device. Nothing you enter is sent, saved, or tracked.

Comparison mode

Same contribution — both put the same dollars in the account; Traditional's tax saving is invested in a taxable side account. Same take-home pay — same out-of-pocket cost; the pre-tax break lets you contribute more to Traditional.

Current age

Retirement age

Annual contribution

Your own annual contribution (gross). In "same contribution" mode this is the amount that goes into either account.

Current marginal tax rate

Combined federal + state estimate. Find your bracket.

Retirement marginal tax rate

Your best guess for retirement — the key uncertainty. Higher than today favors Roth; lower favors Traditional.

Expected annual return

Advanced settings

Taxable-account tax drag (mode 1)

Approximate tax rate applied to the Traditional side-account's growth in "same contribution" mode. Simplified as a reduction to its effective return. Only affects mode 1.

This models new contributions only — your existing TSP balance is out of scope.

Result

After-tax value at retirement

Agency match is always Traditional

Matching contributions always go into your Traditional balance — even if you contribute only Roth. Most FERS employees end up with some Traditional money regardless, so this is about tax diversification, not all-or-nothing.

Qualified Roth withdrawals

Roth earnings come out tax-free only if the withdrawal is qualified: you're age 59½ or older and the Roth account is at least 5 years old.

2026 Roth catch-up rule (age 50+)

Starting in 2026, catch-up contributions must be Roth for participants whose prior-year Social Security (FICA) wages exceeded $150,000. If that's you, your catch-up dollars will be Roth automatically.

Consider splitting

Because future tax rates are uncertain, many people split contributions between Roth and Traditional to hedge — giving flexibility to manage taxable income in retirement.

How this works

Traditional (pre-tax): you skip taxes on the contribution now, the balance grows tax-deferred, and the entire withdrawal is taxed as ordinary income in retirement.

Roth (after-tax): you pay tax on the contribution now, but qualified withdrawals — including all growth — are tax-free.

The fair comparison depends on what you do with Traditional's tax savings:

Same contribution mode: both options put the same dollars in the TSP. Traditional also produces an up-front tax saving (contribution × your current rate), which we invest in a taxable side account growing at a reduced (tax-dragged) rate. We compare Roth's tax-free total against Traditional's after-tax balance plus that side account.
Same take-home mode: we hold your out-of-pocket cost constant. A Roth dollar costs a full dollar after tax, but the same out-of-pocket buys a larger pre-tax Traditional contribution (contribution ÷ (1 − current rate)). No side account is needed.

The classic rule of thumb: Roth wins if your tax rate in retirement is higher than today; Traditional wins if it's lower.

Reference: TSP — Contribution types.