Neal Caffrey

TSP Loan Repayment Calculator

Calculators

TSP Loan Repayment Calculator

This calculator estimates Thrift Savings Plan (TSP) loan repayment based on official TSP rules and regulations. TSP loans allow federal employees and uniformed service members to borrow from their own contributions and earnings. Two types available: General Purpose (1-5 years, $50 fee, no documentation) and Primary Residence (1-15 years, $100 fee, documentation required) [^119^][^120^]. Minimum loan amount is $1,000. Maximum is the smallest of: (1) your contributions and earnings, (2) 50% of vested balance or $10,000 (whichever is greater), or (3) $50,000 minus highest outstanding loan balance in past 12 months [^121^][^122^][^123^]. Interest rate is fixed at the G Fund rate when loan is processed (currently ~4.625% as of 2025) [^131^]. Payments are deducted from pay and reinvested according to current contribution allocation. If you separate from service with an outstanding loan, you must repay within 90 days or face taxable distribution [^120^][^133^]. Loans reduce retirement savings growth potential. Results are estimates; log into My Account at tsp.gov for actual maximum loan amount and official repayment terms.

What Is a TSP Loan?

A TSP loan allows federal employees and service members to borrow money from their own retirement account.

There are two main types:

  • General Purpose Loan
    • срок: 1 to 5 years
    • fee: $50
    • no documentation required
  • Primary Residence Loan
    • срок: 1 to 15 years
    • fee: $100
    • requires documentation

The calculator you shared supports both types and automatically applies the correct limits and fees.

What Does a TSP Loan Calculator Do?

A good calculator does more than just basic math. It gives a full picture of your loan.

Key outputs include:

  • Payment per period
  • Total interest paid
  • Total repayment amount
  • Number of payments
  • Processing fee
  • Opportunity cost (lost investment growth)
  • Maximum loan eligibility

Your calculator includes all of these, which makes it very practical and realistic.

Inputs Explained (Simple Breakdown)

Let’s go through each field so it’s easy to understand.

1. Loan Type

You choose between general purpose or residential.
This affects:

  • maximum repayment term
  • processing fee

2. Loan Amount

  • Minimum: $1,000
  • Maximum: $50,000 (with conditions)

This is the amount you want to borrow.

3. Interest Rate

  • Fixed for the life of the loan
  • Based on the G Fund rate

Your calculator uses a default of 4.625%, which matches recent rates.

4. Repayment Term

How long you will take to repay the loan.

  • General: up to 5 years
  • Residential: up to 15 years

5. Pay Frequency

This controls how often payments are made:

  • Weekly (52 payments/year)
  • Biweekly (26)
  • Semimonthly (24)
  • Monthly (12)

More frequent payments usually reduce total interest slightly.

6. Account Balance

Used to calculate:

  • maximum loan eligibility
  • opportunity cost

7. Outstanding Loan Balance

If you already have a loan, this reduces how much more you can borrow.

8. Contribution Allocation

This shows where repayments are invested (often the G Fund).
It affects long-term growth but not the loan payment itself.

How the Calculator Works (Behind the Scenes)

The calculator uses a standard loan formula.

Step 1: Calculate periodic interest rate

periodic rate = annual rate ÷ pay frequency

Step 2: Calculate number of payments

total payments = years × payments per year

Step 3: Calculate payment amount

If interest exists:

payment = loan × [r(1+r)^n] / [(1+r)^n − 1]

If interest is 0:

payment = loan ÷ number of payments

This is exactly how your calculator computes the payment amount.

Understanding the Results

Once you click “Calculate TSP Loan”, you’ll see several outputs.

Payment Amount

This is what gets deducted from your paycheck.

Total Interest Paid

Even though you pay interest to yourself, it still matters.
It reduces your short-term cash flow.

Total Repayment

Principal + interest combined.

Processing Fee

  • $50 or $100 depending on loan type
  • deducted from your loan

Net Loan Amount

What you actually receive after the fee.

Opportunity Cost (Very Important)

This is one of the best features in your calculator.

It estimates how much you lose by taking money out of investments.

Example:

  • Market growth assumption: 7%
  • Loan rate: ~4.6%

The difference is your lost potential earnings.

This is often the hidden cost people ignore.

Maximum Loan Eligibility

The calculator checks three rules:

  1. Your available balance
  2. 50% of vested balance (or $10,000 minimum rule)
  3. $50,000 cap

Then it shows the lowest value.

If you exceed it, you get a warning.

Example Scenario

Let’s say:

  • Loan: $20,000
  • Rate: 4.625%
  • Term: 5 years
  • Frequency: biweekly

You might see:

  • Payment: ~$175–$185
  • Total interest: ~$2,500–$3,000
  • Opportunity cost: much higher depending on market growth

This shows why a TSP loan feels cheap but can cost more in the long run.

Pros and Cons of TSP Loans

Pros

  • No credit check
  • Lower interest rates
  • Interest goes back to your account
  • Easy payroll deductions

Cons

  • Lost investment growth
  • Double taxation on interest
  • Risk if you leave your job
  • Reduces retirement savings

When Should You Use a TSP Loan Calculator?

Use it when:

  • You are planning to borrow from TSP
  • You want to compare loan terms
  • You want to understand real cost vs benefits
  • You are deciding between TSP loan and personal loan

Practical Tips

  • Keep the loan term as short as possible
  • Borrow only what you truly need
  • Always check opportunity cost
  • Avoid borrowing during strong market growth periods
  • Plan for repayment if you change jobs