Is Roth or traditional TSP better?

It comes down to one comparison: the tax rate your traditional contribution saves you today against the tax rate you expect to pay when you withdraw. If your retirement rate will be higher, Roth wins. If it will be lower, traditional wins. The break-even point is the rate the deduction actually saves you now, and this calculator computes that figure from the 2026 brackets in IRS Rev. Proc. 2025-32 rather than guessing at your bracket. Years until retirement and your expected return do not change the break-even, because they scale both sides of the comparison equally.

Does the agency match go to Roth if I contribute Roth?

No. TSP states it plainly: "Agency or service contributions always go into your traditional balance, regardless of your contribution choice." That covers both the Agency Automatic 1 percent and the matching contributions. Your Roth contributions still earn the full match, the match just lands on the traditional side and gets taxed when you withdraw it. Because that is true under either election, the match does not change the Roth versus traditional answer.

What is the 2026 TSP contribution limit?

IRS Notice 2025-67 set the 2026 elective deferral limit under section 402(g) at $24,500, up from $23,500. The age 50 catch-up is $8,000, and the higher catch-up for anyone who is 60, 61, 62 or 63 during 2026 stays at $11,250. That puts the ceiling at $24,500 under age 50, $32,500 at 50 through 59 and 64 and over, and $35,750 at ages 60 through 63. Agency contributions sit outside the 402(g) limit.

Why does Roth cost more take-home pay for the same contribution?

A traditional contribution comes out before federal income tax, so a $5,000 contribution in the 22 percent bracket only reduces your paycheck by $3,900. A Roth contribution of the same $5,000 reduces it by the full $5,000, because the tax is already paid. That is why this calculator shows two framings. Same dollars into the TSP means Roth shelters more real money but costs more take-home today. Same take-home pay means the Roth contribution is smaller, and the comparison becomes a clean bet on tax rates.

When are Roth TSP earnings tax free?

Your own Roth contributions always come out tax free. The earnings on them are tax free only in a qualified distribution, which TSP describes as requiring both conditions: five years have passed since January 1 of the calendar year of your first Roth TSP contribution, and you are at least 59 and a half, permanently disabled, or deceased. The five year clock starts on January 1 of that first contribution year, not on the contribution date, which means a December contribution buys you almost a free year on the clock.

What marginal rate should I use for retirement?

Add up what you expect to be taxable: your FERS annuity, the taxable share of Social Security, any TSP withdrawals from the traditional side, and other income. Most career federal retirees land in the 12 or 22 percent bracket. Remember that your FERS annuity alone often fills the lower brackets, so the first dollar of a traditional TSP withdrawal is usually taxed at your top rate, not your average rate. If you expect to be in a 22 percent bracket in retirement and your deduction only saves 12 percent today, Roth is the better bet.

Can I split my contributions between Roth and traditional?

Yes. TSP lets you direct any share of your own contributions to either balance, and you can change the split at any time through your payroll system. Splitting is a reasonable answer when you genuinely do not know which direction rates will move, and it is the only answer if you want some tax-free income to draw on in a year when a large withdrawal would push you into a higher bracket or across an IRMAA line.

Calculator

Roth vs Traditional TSP

One number decides this: the retirement tax rate at which Roth starts beating traditional. This tool finds it from the 2026 IRS brackets, then shows the after-tax result both ways, because Roth costs more take-home pay today for the same contribution.

Reviewed by Jonathan D., 20-year federal employee · Formulas verified against IRS.gov and TSP.gov · Updated October 2026

Rule snapshot

Reviewed October 3, 2026. Sources: IRS Notice 2025-67 (2026 limits) · IRS Rev. Proc. 2025-32 (2026 brackets) · TSP: traditional and Roth contributions · 26 U.S.C. 402A. Your inputs stay in your browser. Nothing is sent to a server and nothing is saved.

Your pay and your election

Annual basic payBasic pay including locality. Not awards or overtime.

Your contribution, percent of pay5 percent draws the full agency match.

Filing statusSets the 2026 bracket table used for your current rate.

Other household taxable incomeSpouse pay, interest, rent. Leave at 0 if none.

Retirement assumptions

Your age this yearAge on December 31. Drives catch-up eligibility.

Years until you start withdrawing

Expected annual return, percentNominal, before inflation. Same rate is used on both sides.

Marginal tax rate you expect in retirement, percentCount your FERS annuity and Social Security. Most career feds land in the 12 or 22 percent bracket.

Catch-up contributions (age 50 and over)

Catch-up dollars for 2026Available starting in the year you turn 50.

2025 Social Security wages (W-2 box 3)Above $150,000 and your catch-up must be Roth in 2026.

It is a tie on these numbers. Your retirement rate of 22.0 percent matches the 22.0 percent the deduction saves you now, so either election ends in the same place. Break-even retirement tax rate 22 percent.

Break-even retirement tax rate

22.00%

Pay more than this in retirement and Roth wins. Pay less and traditional wins.

It is a tie on these numbers. Your retirement rate of 22.0 percent matches the 22.0 percent the deduction saves you now, so either election ends in the same place.

Same take-home pay today

Same take-home pay today: contributions, take-home cost, and after-tax value at retirement
Measure	Traditional	Roth
Contributed per year	$5,000	$3,900
Take-home given up per year	$3,900	$3,900
Balance at retirement	$183,928	$143,464
After tax, yours to spend	$143,464	$143,464

Holding your paycheck steady, Roth ends $0 ahead after tax because your retirement rate is above the 22.0 percent you save today.

Same dollars into the TSP

Same dollars into the TSP: contributions, take-home cost, and after-tax value at retirement
Measure	Traditional	Roth
Contributed per year	$5,000	$5,000
Take-home given up per year	$3,900	$5,000
Balance at retirement	$183,928	$183,928
After tax, yours to spend	$143,464	$183,928

Putting the same $5,000 a year into Roth leaves $40,464 more after tax, because the Roth dollars are already taxed. It costs $1,100 more take-home pay each year.

Agency money is traditional either way. Your agency puts $5,000 a year in (5.0 percent of pay: $1,000 automatic plus $4,000 matching). It goes to the traditional balance even for a Roth contributor, grows to $183,928, and is taxed at withdrawal in both scenarios. That is why it does not change the answer above.

How we got this

Taxable income before any TSP deduction: $100,000 income minus the $16,100 standard deduction = $83,900. That lands in the 22 percent bracket (IRS Rev. Proc. 2025-32).
Your $5,000 traditional contribution cuts your 2026 federal income tax by $1,100, which is 22.00 percent of the contribution.
Traditional employee balance after 20 years at 6 percent: $183,928. Taxed at 22 percent it is worth $143,464.
Same dollars in Roth: $183,928, all of it yours. Extra take-home cost: $1,100 a year.
Same take-home instead: $3,900 a year into Roth grows to $143,464, all of it yours.
Break-even retirement rate is 22.00 percent. Above that, Roth wins. Below it, traditional wins. Years and return do not move this number because they scale both sides equally.
Agency money (5.0 percent of pay, $5,000 a year) is traditional either way and grows to $183,928. It is taxed at withdrawal in both scenarios, so it does not change the choice.

Roth earnings come out tax free only if the withdrawal is qualified: five years since January 1 of the year of your first Roth TSP contribution, and age 59 and a half, disability, or death (26 U.S.C. 402A(d)(2)).

What this models, and what it does not

Scope of the Roth versus traditional TSP calculator: what the engine accounts for and the limits you should know before acting on the result
Modeled	Not modeled
2026 federal income tax brackets and standard deduction for all four filing statuses, from IRS Rev. Proc. 2025-32.	State and local income tax. Several states exempt some retirement income, which can move the break-even by several points.
The blended rate your traditional contribution actually saves, including the case where the contribution crosses a bracket line.	Itemized deductions, credits, the qualified business income deduction, and the extra standard deduction for age 65 and over.
The 2026 elective deferral limit of $24,500 plus the $8,000 and $11,250 catch-up limits, applied to your inputs.	The section 415(c) annual additions limit of $72,000, which caps employee plus agency dollars in a single year.
The SECURE 2.0 section 603 test: prior-year Social Security wages above $150,000 force your catch-up into Roth.	Combat-zone tax-exempt pay, where TSP requires Roth catch-up regardless of income.
Agency automatic 1 percent and matching dollars, always traditional, and the match you forfeit by contributing under 5 percent.	Mid-year pay raises, step increases, promotions, and any year when you change your contribution percent.
A single flat nominal return applied to both elections, with contributions landing at the end of each year.	Market sequence risk, fund expense differences, and inflation. All figures are nominal future dollars.
A single flat retirement marginal rate on the traditional balance.	Bracket changes over time, IRMAA surcharges, the taxable share of Social Security, and required minimum distributions forcing income you did not want.

Precision limit: dollar figures are rounded to the cent inside the engine and displayed to the dollar, so a long projection can differ by a few dollars from a spreadsheet that compounds monthly. This is an estimate, not tax advice. Talk to a tax professional before changing a large election.

The only thing that decides this

Traditional TSP skips the tax now and pays it later. Roth TSP pays the tax now and skips it later. Hold your paycheck steady and the whole question collapses to a rate comparison: whichever rate is lower is the one you want to pay. The break-even figure at the top of this page is the rate your traditional deduction actually saves you in 2026. Expect a higher rate in retirement and Roth is the better bet. Expect a lower one and traditional is.

Notice what is missing from that: your return assumption and your years to retirement. Both scale the Roth side and the traditional side by the same factor, so they cancel. Change the return from 5 percent to 9 percent in the tool and watch the break-even rate hold still. A long horizon does not favor Roth on its own.

Why we show two framings

Contribute $5,000 traditional in the 22 percent bracket and your paycheck drops by $3,900, because the deduction hands $1,100 back. Contribute $5,000 Roth and your paycheck drops by the full $5,000. Those are not the same decision, so comparing them as if they were loads the answer toward Roth.

The same take-home panel keeps your paycheck fixed and shrinks the Roth contribution to match, which isolates the rate bet. The same dollars panel keeps the contribution fixed and shows what Roth really buys you: more sheltered money, at a real cost to this month's budget. If you are already contributing the full $24,500 limit, the second framing is the one that matters, because $24,500 of Roth money is worth more at retirement than $24,500 of traditional money and the limit will not let you make up the difference.

The match is not part of the decision

Agency money is always traditional. TSP puts it in one sentence: agency or service contributions always go into your traditional balance, regardless of your contribution choice. Your Roth contributions still earn every dollar of match. Since that is true under either election, it drops out of the comparison.

What does matter is whether you are capturing the match at all. Five percent of basic pay draws the full 4 percent match plus the 1 percent automatic contribution. Anything under 5 percent leaves money behind, and the tool prints the annual figure you are forfeiting. Fix that before you spend another minute on the Roth question. Our TSP Contribution Calculator works out the per-pay-period figure.

If you are 50 or older in 2026

Part of this choice may already be made for you. Section 603 of the SECURE 2.0 Act requires catch-up contributions to be Roth when your prior-year Social Security wages from your federal employer exceeded an indexed threshold. IRS Notice 2025-67 set that threshold at $150,000 of 2025 wages, and TSP applies the rule from January 1, 2026. Above the line, your $8,000 or $11,250 of catch-up has to go Roth. Your first $24,500 is still your call. Details in our guide to the mandatory Roth catch-up.