TSP Contribution Calculator: Compare Rates, Paychecks, and Agency Match
Use this guide to understand the assumptions, inputs, results, and next steps behind the calculator.
Created by Luis Gonzalez · Last updated July 4, 2026
A TSP contribution rate is the share of eligible pay you direct into the Thrift Savings Plan. Increasing that rate can build retirement savings and may capture more agency matching contributions, but it also reduces current take-home pay. This calculator compares a current contribution rate with a proposed rate, estimates agency match, and approximates the paycheck effect.
With the default inputs—$85,000 annual salary, a current 3% rate, a proposed 5% rate, a 22% federal bracket, a 5% state tax rate, and 26 pay periods—the calculator estimates that increasing the contribution reduces take-home pay by $47.73 per paycheck. The proposed 5% contribution captures 100% of the modeled maximum annual match, or $4,250.
Enter your current and proposed rates
Enter annual salary, current contribution rate, and proposed rate. The calculator uses 26 pay periods by default, representing biweekly payroll. If your agency pays on a different schedule, update that input so the per-paycheck estimate matches your actual pay frequency.
The federal bracket and state tax rate estimate tax effects on traditional contributions. Set the Roth portion if some or all contributions are Roth. The service type and catch-up option affect the applicable match or contribution limits in the calculator; confirm your plan rules and eligibility before relying on the estimate.
Default example: paycheck cost and match captured
At $85,000 salary, a 3% contribution is $2,550 per year. At 5%, the annual contribution is $4,250. The difference is $1,700 annually.
Current contribution = $85,000 × 3% = $2,550 per year
Proposed contribution = $85,000 × 5% = $4,250 per year
With 26 pay periods, the proposed contribution per paycheck is:
$4,250 ÷ 26 = $163.46
The current contribution is $2,550 ÷ 26, or about $98.08 per paycheck. The take-home estimate changes from $2,314.94 to $2,267.21, so the paycheck impact is:
$2,267.21 − $2,314.94 = −$47.73 per paycheck
This estimate reflects the calculator’s assumptions: traditional contributions, a combined federal and state tax rate of 27%, and the selected pay schedule. Actual net pay may also include FICA taxes, insurance premiums, other deductions, tax credits, and payroll-specific rules.
| Contribution rate | Annual employee contribution | Modeled agency match | Combined annual amount |
|---|---|---|---|
| 3% | $2,550 | $3,400 | $5,950 |
| 5% | $4,250 | $4,250 | $8,500 |
| 8% | $6,800 | $4,250 | $11,050 |
The match tops out at the 5% contribution rate in the calculator’s modeled FERS schedule. A contribution above 5% can still increase your own retirement savings but does not add more match under that formula.
Understand the modeled TSP matching rules
The calculator uses a FERS-style match formula: a 1% automatic agency contribution, dollar-for-dollar matching on the first 3% of pay you contribute, and 50 cents per dollar on the next 2%. At a 3% contribution rate on $85,000, the modeled match is $850 automatic plus $2,550 dollar-for-dollar, or $3,400. At 5%, the additional 2% contribution receives a 50% match of $850, bringing the total to $4,250.
3% employee rate: $850 automatic + $2,550 match = $3,400
5% employee rate: $850 + $2,550 + $850 = $4,250
The “Annual Match Captured” result compares the proposed match with the calculator’s maximum modeled match. The default 5% proposal captures 100%. That result is not a rating of your overall retirement readiness; it only measures the proposed rate against the model’s matching ceiling.
The actual TSP contribution structure depends on service type and eligibility. Check the TSP’s contribution types and matching guidance and your payroll statement. A TSP match calculator can help isolate match assumptions, while the TSP calculator projects account growth over time.
Formula: paycheck impact and annual match
For traditional contributions, the calculator estimates tax savings by reducing taxable income by the pretax portion of the contribution. It combines the entered federal and state rates for this simplified estimate.
Contribution per paycheck = annual contribution ÷ pay periods
Estimated take-home pay = gross pay − estimated taxes − contribution
Paycheck impact = proposed take-home pay − current take-home pay
The match formula in the default FERS model is:
Agency match = 1% automatic + 100% of first 3% contributed + 50% of next 2% contributed
These estimates do not constitute a full paycheck calculation. Traditional contributions can reduce income subject to income tax, but generally do not reduce Social Security and Medicare payroll taxes. Roth contributions are treated differently for current income-tax purposes; the calculator applies the Roth percentage to its simplified tax estimate.
2026 TSP contribution limits
For 2026, the employee elective deferral limit for TSP and most 401(k), 403(b), and 457(b) plans is $24,500. Eligible participants age 50 or older may generally contribute an additional $8,000. Eligible participants ages 60–63 may have an $11,250 catch-up limit under SECURE 2.0. Check current rules and eligibility with the IRS and TSP.
The default $4,250 proposed contribution is below the regular limit. At higher salary or contribution rates, the calculator caps employee contributions at the applicable limit. Agency contributions are not the same as employee deferrals, so do not use the employee limit as a cap on every source of plan funding.
If your goal is to increase retirement savings beyond the match, compare the paycheck effect with a TSP contribution calculator or a 401(k) contribution calculator. If you are deciding whether to contribute to a Roth account, compare a Roth 401(k) contribution calculator with the traditional contribution estimate.
FAQs about TSP contribution rates
How much should I contribute to the TSP?
A common starting point is to contribute enough to receive the full matching contribution available to you, if your budget allows. Beyond that, choose a rate that fits your cash flow, debt obligations, and retirement timeline.
Does increasing my contribution by 2% reduce take-home pay by 2%?
No. The gross contribution increases by 2% of salary, but traditional contributions may reduce income taxes. The exact take-home change also depends on other payroll taxes and deductions. In the default estimate, the change from 3% to 5% is −$47.73 per paycheck, not 2% of gross paycheck pay.
Is the 5% match rule the same for every TSP participant?
No. The calculator models a FERS-style match. Military service rules and individual eligibility can differ. Verify the formula that applies to your service and account.
Should I choose traditional or Roth TSP contributions?
Traditional contributions generally offer a current income-tax benefit, while Roth contributions are made after tax and can provide tax-free qualified withdrawals. The decision depends on current and future tax rates, withdrawal plans, and other income. The calculator does not forecast your lifetime tax bill.
Should I raise my contribution rate or build an emergency fund first?
Both goals matter. A higher TSP rate can capture match and build long-term savings, while an emergency fund can help prevent debt or early retirement withdrawals after an unexpected expense. Compare the value of available matching contributions with your cash reserve needs and high-interest debt.
Does the calculator include all payroll deductions?
No. It estimates the impact of the TSP contribution using the supplied tax rates and pay periods. It does not account for every deduction, tax credit, payroll tax, or benefit premium.
What if I contribute more than the annual limit?
The calculator caps the employee contribution at its selected limit. If you contribute to multiple eligible workplace plans, the limits and coordination rules can be complicated. Review current IRS rules and payroll records to avoid excess deferrals.
Next steps: test a contribution increase
Try increasing your proposed rate by one percentage point at a time and compare the reduction in take-home pay with additional annual savings and match. Check the annualized impact as well as the per-paycheck figure, then confirm the match on your statement. For account-growth projections, use the TSP growth calculator; for future distributions, use the TSP withdrawal calculator.
A contribution decision is only one part of retirement planning. Review required minimum distributions and estimate whether your projected account balance can support the retirement income you expect. A retirement withdrawal strategy calculator can help compare account drawdown approaches.