TSP Retirement Calculator Guide 2026: Limits, Match, and Projections

The Thrift Savings Plan is the federal government's version of a 401(k), and for most civilian and uniformed service members it quietly becomes the largest asset they own. The reasons are structural: contributions come out of pay automatically, expenses stay low, and — under FERS — the agency adds money on top of whatever you defer. None of that tells you what your balance might be at retirement, though, and that is the question a TSP retirement calculator exists to answer. This guide covers the inputs that matter: contribution limits and how they roll forward, the 1% automatic and matching contributions, traditional versus Roth, the funds, and how projections turn monthly deferrals into a number you can plan around. Estimates, not guarantees — but disciplined ones.

CHAPTER 01What the TSP Is — and Why It Starts at 5%

The TSP is a defined-contribution plan for federal employees and uniformed services, administered as a low-cost sibling of private-sector 401(k) plans. Under FERS, your retirement income has three legs — the basic annuity, Social Security, and the TSP — and the TSP is the leg you control most directly. Contribution percentages come out of each paycheck before you can spend them, which is quietly the most powerful feature of the whole system.

The number to internalize is 5%. When you defer at least 5% of basic pay, the agency contributes its maximum: an automatic 1% plus matching dollars that together equal another 4%. Below 5%, part of the match is left on the table every single pay period. No fund choice or market timing replicates an immediate, guaranteed return of that shape, which is why every calculator scenario in this series assumes the match is captured first.

Contributions can be split between traditional (pre-tax) and Roth (after-tax) TSP in any proportion, and investment elections apply across both. Payroll changes are made through your agency's electronic system and generally take a pay period or two to land, so plan changes around the start of a year rather than reacting mid-month.

CHAPTER 02Contribution Limits and How They Roll Forward

For 2025, the elective deferral limit is $23,500, with an additional catch-up of $7,500 for contributors age 50 and over. Participants in the 60-to-63 age window get a higher special catch-up — $11,250 under the 2025 figures — which replaces the standard catch-up amount for those years. Limits are set annually by the IRS and adjust over time, so treat these as recent anchors and check tsp.gov for the current-year numbers before you set a payroll election.

Two practical wrinkles matter for planning. First, the deferral limit is a combined ceiling: traditional and Roth contributions share it. Second, catch-up contributions are opt-in each year — they do not happen automatically when you turn 50, so the birthday is the trigger to file the election, not the payroll office. Both wrinkles are payroll mechanics rather than finance, which means both are fixable in minutes through your agency's electronic system.

For a calculator, what matters is the annual ceiling converted to per-paycheck reality. A $23,500 goal over 26 pay periods is about $904 per pay period; hitting a limit early in the year can pause agency matching for the remainder of the year under some payroll setups, which is why many planners deliberately spread contributions evenly rather than front-loading.

CHAPTER 03The Match: 1% Automatic, Up to 4% Matched

The FERS agency contribution has two parts. The automatic 1% of basic pay goes in whether you contribute or not. On top of that, the first 3% you defer is matched dollar for dollar, and the next 2% is matched at fifty cents on the dollar. Contribute 5% and the agency adds 5% — doubling your money before any investment return exists.

The arithmetic is worth seeing once in raw dollars. At an $80,000 salary contributing 5%: you put in $4,000; the agency adds its automatic $800 plus $3,200 of match, another $4,000. Total flowing into the plan: $8,000 a year from a $4,000 payroll deduction. That is a 100% immediate return on the matched dollars, which is why this guide hedges market figures freely but never hedges the match.

In the uniformed services the Blended Retirement System works on the same shape, with some differences in vesting timing and continuation pay for the military. If you are BRS-eligible, the 5% target still applies as the planning default. Vesting of agency contributions follows FERS/BRS rules, while your own contributions are yours immediately.

CHAPTER 04Traditional vs. Roth TSP

Traditional TSP deferrals come out of pay before federal income tax, lowering taxable income now; withdrawals in retirement are taxed as ordinary income. Roth TSP deferrals come out after tax; qualified withdrawals — typically age 59½ or later, with the five-year rule satisfied — come out tax-free, including the earnings. Neither is universally better; they are two different bets about your tax rate today versus your tax rate later.

A useful simplification: early-career employees in lower brackets often lean Roth, mid-to-late-career earners in higher brackets often lean traditional, and many do both. State tax treatment and retirement location add nuance, as does the fact that TSP balances eventually interact with required minimum distribution rules. A calculator can show the growth path for either; it cannot know your future bracket, so treat any Roth-versus-traditional verdict as scenario, not prescription.

One structural point people miss: Roth TSP is not a Roth IRA. Limits, withdrawal rules, and income eligibility are separate systems, and the TSP deferral limit is shared across your traditional and Roth contributions combined. Confusing the two leads to wrong annual targets — a common mistake covered in the companion piece.

CHAPTER 05The Funds and Lifecycle Funds

The core menu is five index funds: G (government securities, the stable option), F (fixed income), C (large-cap US stocks), S (small- and mid-cap US stocks), and I (international stocks), plus Lifecycle (L) funds that hold all five in an age-appropriate mix and adjust over time. Expenses across the lineup have historically been among the lowest in any retirement plan, though you should verify current expense ratios on tsp.gov rather than trusting a blog's numbers.

Allocation is the biggest lever a calculator cannot responsibly pick for you: long-run growth assumptions of 5–8% a year describe stock-heavy mixes, while conservative mixes plausibly earn less with less volatility. That is why every projection in this series states its assumed return out loud. A plan earning 4% and a plan earning 7% are not small variations of each other over thirty years — they are different retirements.

A reasonable workflow: pick a target date L fund and treat it as the default decision, or build your own mix from the five funds if you want the control. Whichever you choose, the calculator's job is to project outcomes under a stated mix and return — the mix itself is a decision you own, ideally reviewed annually rather than during market storms.

CHAPTER 06What a TSP Calculator Actually Models

A TSP retirement calculator takes four families of inputs: current balance, contribution rate (yours plus the agency's), assumed annual return, and years to retirement. It then compounds the balance forward, typically monthly, and reports a projected total — sometimes alongside contributions-only totals so you can see how much of the final number is growth. Some models add salary growth, which changes results meaningfully; flat-contribution models are more conservative by construction.

The honest caveats live in the assumptions. A 7% return is a planning average, not a promise; sequence risk means real portfolios zigzag around the average; and inflation separates nominal from real dollars — $1 million in 30 years is not $1 million of today's purchasing power. Good calculators show real (inflation-adjusted) figures or at least flag the distinction; every figure in this series is a hedged nominal estimate unless stated otherwise.

Use the tool the way actuaries do: run three scenarios (conservative, middle, optimistic), look at the spread rather than the middle number, and let the spread drive behavior. If the low scenario still funds your plan, the uncertainty is survivable; if only the high scenario does, the plan is fragile and the contribution rate, not the projection, is the lever to move.

CHAPTER 07Withdrawals: Getting Money Out

Accumulation rules get the attention, but withdrawal rules shape real plans. In general, separating from federal service opens options: a lump sum, monthly payments, an annuity purchase, or combinations, with tax treatment depending on traditional versus Roth money and your age. In-service withdrawals are limited — loans exist under rules but carry real costs — and early access before separation is deliberately restrictive.

Age rules matter here. Money withdrawn before 59½ generally carries a 10% early-distribution penalty with exceptions; separation in or after the year you turn 55 is one of the classic exceptions for employer plans, though details vary by situation and this guide hedges them deliberately. Required minimum distributions eventually apply to traditional money. The TSP's own withdrawal materials are the authority; treat any blog summary, including this one, as orientation only.

A TSP retirement calculator helps most here in reverse: starting from a target income, it can estimate the balance needed to support it under a chosen withdrawal rate. Commonly cited rates around 4% a year are planning heuristics, not rules. If a projected balance supports 4% of itself at your target income, you have a working hypothesis; if not, the years-to-go or contribution-rate inputs are where the fix begins.

🔑 Key takeaways

• Contribute 5% of basic pay first: the agency's 1% automatic plus match tops you up to 10% of pay flowing in.
• 2025 anchors: $23,500 elective limit, $7,500 catch-up at 50+, and an $11,250 special catch-up for ages 60–63 — verify current-year figures on tsp.gov.
• The deferral limit is shared between traditional and Roth TSP; the two are a tax-timing choice, not separate accounts with separate ceilings.
• Every projection is only as honest as its stated return assumption — run conservative, middle, and optimistic scenarios and plan around the spread.
• Growth assumptions of 5–8% describe stock-heavy mixes; conservative mixes plausibly earn less with less volatility.
• Withdrawal rules — penalties before 59½, exceptions at 55, eventual RMDs — belong in the plan before retirement, not after.

❓ Frequently asked questions

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