Roth Tsp Calculator

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Project your Roth TSP to retirement with monthly compounding, fold in the agency match (enter 5% for the full FERS match) alongside your Roth balance, and get a straight answer to the question that matters: Roth or traditional? The comparison runs at equal out-of-pocket cost, so the verdict means something. Projection only, not financial advice; not affiliated with the TSP or the FRTIB.

Roth TSP Calculator
Monthly-compounded growth projection with agency match and a Roth vs traditional verdict
Enter valid ages, amounts, and rates. Retirement age must exceed current age.
Roth TSP projection

Projection only, not financial advice. Assumes constant monthly contributions and a constant annual return compounded monthly. The agency match always goes to traditional, even on Roth contributions. Tax rules change; confirm with a tax professional. This tool is not affiliated with the Thrift Savings Plan or the FRTIB.

Quick Answer

A 30-year-old with a $10,000 Roth balance, $500/month contributions, and 7% annual return reaches roughly $1,020,842 tax-free at 65 ($220,000 contributed, about $800,842 in earnings). The 5% agency match on an $80,000 salary compounds to another $603,854 in the traditional bucket, for $1,624,695 combined. At 22% now vs 18% in retirement, traditional wins the equal-out-of-pocket comparison: $952,231 of after-tax spending power vs $905,780 from the Roth side. Change the rates and the verdict flips. The calculator above is pre-filled with exactly this scenario.

Key takeaways

  • The match always lands in traditional, even if 100% of your own money goes to Roth, so a "100% Roth" fed still retires with a split account.
  • The Roth vs traditional question has one deciding factor: your marginal tax rate now vs your marginal rate in retirement. Everything else is arithmetic.
  • With equal tax rates the two are mathematically identical: a $500/month Roth contribution and its $641.03 pre-tax traditional equivalent grow to the same spendable number.
  • Roth TSP money itself is exempt from RMDs under SECURE 2.0, while the traditional match money counts toward them. That split is why the calculator reports the combined balance with each bucket labelled.
On this page

How to use the Roth TSP calculator

Enter your figures, click Calculate, and read three things: your Roth balance at retirement, the agency match grown beside it, and the verdict. The results stay hidden until you calculate; the fields come pre-filled with the worked example.

  1. Ages and balance first: current age, retirement age, and what is already in your Roth TSP. The months between the two ages are what compound.
  2. Monthly contribution, catch-up and return: your after-tax monthly amount plus the assumed annual return, compounded monthly with each contribution treated as landing at the start of the month. If you are 50 or older, add a monthly catch-up amount in the catch-up field; the 2026 catch-up room is $8,000 a year (about $666.67 a month) on top of the $24,500 base, and the tool warns you if base plus catch-up passes the $32,500 ceiling for your age, or if you enter a catch-up before 50.
  3. Salary and match: annual basic pay and the agency match rate. FERS employees should use 5% (1% automatic + 4% matching); CSRS employees get no match, so 0.
  4. The two tax rates: your marginal rate today and the one you expect in retirement. This pair alone decides the verdict, so try a few combinations.

The math: monthly compounding and the equal-out-of-pocket rule

The growth engine is the future value of a lump sum plus an annuity-due, compounded monthly. The annuity-due detail matters: contributions are treated as arriving at the start of each month, so each one earns one extra month of growth.

FV = Balance × (1+r)n + PMT × [((1+r)n − 1) / r] × (1+r)
r = annual return ÷ 12,  n = months between your ages,  PMT = monthly contribution

The comparison is where this tool earns its keep. Most Roth-vs-traditional arguments quietly compare a $500 Roth contribution with a $500 traditional contribution, which is unfair: the Roth dollar cost you tax already paid, so the fair fight is $500 Roth against $500 ÷ (1 − today's rate) pre-tax. At 22%, that is $641.03. The tool grows that equivalent with the same monthly factor, taxes the result at your retirement rate, and declares the winner on spendable dollars, not on account balance.

Worked example, verified against the tool

The pre-filled scenario (30 to 65, $10,000 balance, $500/month, 7%, $80,000 salary, 5% match, 22% now, 18% in retirement) compounds over 420 months at 0.5833% a month. The balance grows to about $115,062 and the contributions to about $905,780, for a Roth total of $1,020,841.89 against $220,000 of contributions, so earnings are $800,841.89. The match side ($333.33/month) becomes $603,853.58 of traditional money, for a combined $1,624,695.48.

The verdict deserves its own table, because this is the part people get wrong.

Tax now / in retirementRoth spendableTraditional spendableWinner
22% / 18%$905,780$952,231Traditional
18% / 24%$905,780$839,504Roth
28% / 18%$905,780$1,031,583Traditional
22% / 22%$905,780$905,780Dead even

Notice the Roth column never moves: the Roth spendable number depends only on contributions and growth, because the tax was already paid. The traditional column swings with both rates, which is why "which rate is higher in retirement" is genuinely the entire question. Run your own numbers in the calculator, then sanity-check the growth side against a plain backward compound interest calculator if you want a second opinion on the compounding.

The agency match always goes to traditional

This is the single most misunderstood TSP mechanic, and the tool gets it right: every agency dollar, automatic 1% and matching contributions alike, is deposited into the traditional balance, even when 100% of your own contributions go to Roth. Federal regulation, not plan policy, is why; the government will not pay the tax for you by routing agency money into Roth. So a "100% Roth" contributor still retires with a meaningful traditional balance, which grows tax-deferred and is taxed as ordinary income on withdrawal.

The FERS schedule: 1% automatic on basic pay every pay period whether you contribute or not, plus dollar-for-dollar matching on the first 3% you defer and 50 cents on the dollar for the next 2%. Contribute 5% and the agency adds 5% total; more than 5% buys no further agency money. Run the TSP matching calculator and you will get the same $333.33/month on the $80,000 example here.

Roth vs traditional: the one-line rule

Expect a lower rate in retirement than today, lean traditional. Expect a higher rate in retirement, lean Roth. Expect the same rate, stop deliberating, because the two are mathematically identical and the decision is a coin flip.

Where feds actually land: a FERS pension, Social Security, and traditional TSP distributions stack in retirement, and many career employees end up in a higher bracket than they expected, which is exactly where paying tax now wins. The counter-case is retiring early to a low bracket or moving from a high-tax state to a no-income-tax state, where the deduction today is worth more. Since the TSP launched in-plan Roth conversions in January 2026, there is also a third lever: contribute traditional now, then convert in low-income years later, though each conversion must be at least $500 and you must keep $500 in each traditional source. If you also hold a Roth IRA alongside your TSP, its conversion math is modelled separately by the IRA conversion to Roth calculator.

What competing calculators miss

Most TSP tools stop at the growth projection, and most Roth tools stop at generic 401(k) math. The gaps, one by one:

  • Generic TSP growth calculators (CalculatorOV and similar): compound balance + contributions with a frequency choice, but no Roth vs traditional comparison and no agency-match compounding, just a lump annual contribution. You get a balance number and no decision help.
  • The TSP's own official Roth in-plan conversion calculator (launched 2026): genuinely useful for one job, estimating the tax bill on converting traditional dollars to Roth, but it is a conversion tool, not a lifetime contribution-growth projector.
  • Contribution optimizers (Federal Warrior's TSP optimizer): excellent on per-pay-period targets, the 5% match floor, and the SECURE 2.0 mandatory-Roth catch-up rule for high earners, but they optimize what you put in this year, not what it becomes by retirement.
  • IRA conversion calculators: model IRA-to-Roth math beautifully, but TSP is not an IRA: no agency match exists on the IRA side, and TSP withdrawal and conversion rules differ.
  • The gap this page fills: monthly-compounded growth of your actual Roth contributions, the agency match compounded alongside (at the match percentage you enter), and a fair-fight Roth vs traditional verdict that prices the upfront deduction correctly, with the assumptions stated plainly under the card.

2026 TSP contribution limits and catch-up

For 2026 the elective deferral limit is $24,500 a year across all your TSP contributions, rising to $32,500 at age 50 and over with the $8,000 catch-up. The calculator tests your monthly base contribution plus catch-up, times twelve, against the limit for your age and warns you when you pass it, while still projecting the full amount you entered. A catch-up entered before age 50 draws its own warning, since catch-up room starts at 50. The super catch-up of $11,250 for ages 60 to 63 that applies to some workplace plans is not modelled here, because its applicability to the TSP was not established for this page; the figures above are the $24,500 base and the $8,000 standard catch-up only. Savers comparing a TSP with an IRA can run the same catch-up logic in our Roth IRA calculator, where the 2026 figures are $7,500 plus a $1,100 catch-up.

Frequently asked questions

It depends on your tax rates, not on your balance. If your marginal rate in retirement will be higher than today's, Roth leaves you more spendable money; if it will be lower, the traditional deduction wins. With equal rates the two are mathematically identical. The calculator's verdict line runs that comparison at equal out-of-pocket cost so you can see which side wins for your own rates.

No. Every agency dollar, the automatic 1% and all matching contributions, is deposited into the traditional balance, even if 100% of your own contributions go to Roth. That is a federal regulatory requirement, not a plan choice. This calculator models the match exactly that way: it compounds beside your Roth money but is reported as traditional and taxable on withdrawal.

Two conditions: you are at least 59 and a half (or meet another qualifying condition), and at least five years have passed since your first Roth TSP contribution. Meet both and withdrawals, earnings included, are tax-free; withdraw earlier and the earnings portion can be taxed and penalized.

Yes. Since January 2026 the TSP offers in-plan Roth conversions, moving money from your traditional balance to your Roth balance inside the plan with no rollover to an IRA. Each conversion must be at least $500, you can do up to 26 per year, and you must keep at least $500 in each traditional contribution source. The converted amount is taxable income in the year of conversion.

The match and its earnings sit in your traditional balance, so they are taxed as ordinary income when withdrawn, and they count toward required minimum distributions (see the TSP RMD calculator for how those are computed). Roth TSP money itself is exempt from RMDs under SECURE 2.0. That split is why the calculator reports the combined balance with each bucket labelled.

Three practical differences: the TSP has an agency match and no IRA has any match; TSP contribution limits are far higher than IRA limits; and TSP money can only go in through payroll deduction, never from a bank transfer. A Roth IRA accepts transfers from other accounts, while the TSP will not accept a rollover from a Roth IRA.

Constant monthly contributions, a constant annual return compounded monthly, contributions treated as arriving at the start of each month, and a flat match rate applied to a flat salary for the whole horizon. Real careers have raises, contribution changes, and market swings, so treat the number as a scenario, not a forecast. The Roth vs traditional comparison assumes equal out-of-pocket contributions.

Yes, directly. Enter your monthly catch-up in the dedicated catch-up field on top of your base monthly contribution: the 2026 catch-up room is $8,000 a year (about $666.67 a month) on top of the $24,500 base, for a $32,500 ceiling at age 50 and over. The tool checks base plus catch-up, times twelve, against the limit for your age and warns you if you exceed it, or if you enter a catch-up before age 50. It also does not model the SECURE 2.0 rule that high earners must direct catch-up contributions to Roth starting in 2026; the projection math is identical either way, only the tax bucket changes.

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References

  1. FedSmith. Federal Employees Gain Powerful New TSP Feature: Roth In-Plan Conversions Officially Launch. Accessed October 23, 2026.
  2. GovExec. TSP in-plan Roth conversions: Are they right for you? Accessed October 23, 2026.
  3. FFB Benefits Association. A New TSP Tool Makes Roth In-Plan Conversions Easier to Evaluate. Accessed October 23, 2026.
  4. FedWeek (Federal News Network). For TSP, 2026 Brings Higher Investment Limits, In-Plan Roth Conversion Option. Accessed October 23, 2026.
  5. FedWeek (Federal News Network). Roth TSP Balances and In-Plan Conversions. Accessed October 23, 2026.
  6. MyFederalRetirement. Roth TSP In-Plan Conversions: Tax Rules You Need to Know. Accessed October 23, 2026.
  7. LegalClarity. Does TSP Allow Roth Conversions? Rules and How It Works. Accessed October 23, 2026.
  8. LegalClarity. Does TSP Match Roth Contributions? Where the Match Goes. Accessed October 23, 2026.
  9. Federal Warrior. TSP Traditional vs Roth. Accessed October 23, 2026.
  10. Federal Warrior. TSP Contribution Strategy. Accessed October 23, 2026.
  11. Interior Business Center, U.S. Department of the Interior. Benefits Digest: Major TSP Changes for 2026. Accessed October 23, 2026.
  12. LegalClarity. When Did Roth TSP Start? Launch Date and History. Accessed October 23, 2026.
  13. Warrior Retirement. TSP RMDs and the Roth-TSP Exemption: 2026 Rules. Accessed October 23, 2026.

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