New for 2026 · In-plan conversions
Answer five questions and this free TSP Roth conversion calculator gives you the tax bill, the long-run value, and a plain-English verdict — in about thirty seconds.
The worksheet
UPDATES AS YOU TYPEThe verdict
+$28,759
more in your pocket at withdrawal, 15 years from now, after all tax is paid.
Break-even reference: 22%. Estimates only — excludes state tax, the five-year rule and RMD timing.
Side by side over time
This chart tracks the after-tax value of the same money on each path, year by year, using the inputs from the worksheet above. The shaded band between the lines is the projected advantage of converting. Hover or tap any year to see the figures for that year.
Projected after-tax value
Converting to Roth versus staying traditional
A projection, not a promise. It assumes a steady annual growth rate and the flat tax rates you entered, and does not model state tax, the five-year rule, RMD timing, or bracket changes.
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Read next
The calculator gives you a figure. These four short guides give you the reasoning behind it, so you walk into any decision — or any conversation with a tax professional — already knowing the right questions.
01
The 401(k) in-plan Roth conversion, explained
What an in-plan conversion is, how the tax works, and how it differs from rolling money to a Roth IRA.
Read the guide →
02
The backdoor Roth for federal employees
How high earners get money into a Roth IRA, and why keeping pre-tax money in the TSP makes it cleaner.
Read the guide →
03
The five-year rule for Roth TSP conversions
The two separate five-year clocks, and how to avoid tripping a tax or penalty by withdrawing too soon.
Read the guide →
04
How TSP withdrawals are taxed
Traditional versus Roth, withholding, the early-withdrawal penalty, RMDs, and where a conversion helps.
Read the guide →
Background
A Roth in-plan conversion lets you move money from your traditional, pre-tax TSP balance into your Roth, after-tax balance, all inside your Thrift Savings Plan account. You do not withdraw the money or open a separate account. You simply change how it will be taxed later.
The trade is straightforward. You pay ordinary income tax now on the amount you convert, because those dollars have never been taxed. In exchange, that money and all of its future growth can come out tax-free in retirement, provided you meet the holding rules.
This matters for federal employees and military members because the option is new. Starting in 2026, TSP participants can convert traditional balances to Roth directly inside the plan for the first time. Before that, the only way to get TSP money into a Roth was to roll it out to an outside Roth IRA. Because the in-plan feature is so recent, clear guidance built specifically for TSP participants is still thin, which is exactly why this page exists.
New to the idea in general? Our plain-English guide to the 401(k) in-plan Roth conversion explains how it works across employer plans, what the tax looks like, and who tends to benefit. Earning too much to fund a Roth IRA directly? See the backdoor Roth for federal employees.
Method
The worksheet compares two futures for the same block of pre-tax money: converting it to Roth today, or leaving it in the traditional balance and paying tax when you withdraw.
If you pay the tax from outside savings, the full amount you convert stays invested and grows tax-free, so its value at withdrawal is the amount multiplied by your growth over the years you selected. If you instead pay the tax out of the conversion itself, only the after-tax portion lands in the Roth balance and grows.
The same starting amount grows at the same rate, but you owe ordinary income tax when you withdraw. The worksheet applies your expected retirement rate to the ending balance to show what you would actually keep.
The single biggest factor is whether your tax rate in retirement is higher or lower than it is today. If you expect to pay a higher rate later, paying the tax now at a lower rate tends to win. If you expect a lower rate later, waiting tends to win. Paying the conversion tax from outside savings shifts the math further in favor of converting, because more money stays sheltered.
Illustration
Suppose a federal employee converts $50,000 of traditional TSP money. She pays a 22% marginal rate today, expects a 24% rate in retirement, plans to leave the money invested for 15 years, and assumes 6% average annual growth. She pays the conversion tax from savings outside the account.
| Amount converted | $50,000 |
| Federal tax owed this year (22%) | $11,000 |
| Growth over 15 years at 6% | ×2.397 |
| Roth value at withdrawal, tax-free | $119,828 |
| Traditional value after 24% tax | $91,069 |
| Projected advantage of converting | $28,759 |
Because she expects a higher rate in retirement than she pays today, and pays the tax from outside savings, the conversion comes out ahead in this example. Change any input in the worksheet above and the result changes with it.
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Common questions
Thrift Savings Plan participants, which includes most federal civilian employees and members of the uniformed services. The in-plan conversion feature became available inside the TSP in 2026. Confirm your specific eligibility and the current process on the official TSP website before acting.
It can. The amount you convert is added to your taxable income for the year, so a large conversion can move part of your income into a higher bracket. Many people spread conversions across several years to stay within a target bracket. This calculator uses a single flat rate you enter, so if you expect part of a conversion to be taxed at a higher rate, run the numbers using a blended estimate or split the amount.
Paying from savings outside the account is generally the stronger move, because it lets the full converted amount keep growing tax-free. It may also be the required method for an in-plan conversion. Use the toggle in the worksheet to see the difference between the two.
Roth conversions carry holding requirements before earnings can be withdrawn tax-free and penalty-free. Withdrawing converted money too soon can trigger taxes or penalties. Our guide to the five-year rule for Roth TSP conversions walks through both clocks in detail.
No. It estimates federal income tax only, using the rates you enter. State income tax, if it applies where you live, would increase the tax owed on the conversion. Add your state's effect separately when you plan.
No. This is an educational estimate to help you understand the trade-offs. A conversion has lasting tax consequences, so talk with a qualified tax professional or financial planner before you convert. See our editorial standards for how this site is researched and reviewed.
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References
Rules and figures change. Verify current details with the official sources above before making a decision.
Please read
This calculator is provided for general educational purposes only and does not constitute tax, legal, investment, or financial advice. It produces simplified estimates based on the figures you enter and a set of assumptions described on this page.
It does not account for state taxes, the five-year holding rule, required minimum distribution timing, changes in tax law, Medicare premium effects, or the possibility that a conversion pushes you into a higher bracket. Actual results will differ. Investment growth is not guaranteed and past performance does not predict future returns.
Before making any Roth conversion decision, consult a qualified tax professional or financial planner and confirm current rules with the official Thrift Savings Plan and Internal Revenue Service resources listed above.