401k Loan Interest Rates: How They Work and What to Expect

• 401k Expert

Quick Answer: 401k Loan Interest Rates

401k loan interest rates are typically set at the prime rate plus 1-2%. In 2025, this means rates around 8.5% to 10%. Unlike traditional loans, you pay this interest back to your own 401k account. While this sounds like a win, you're paying with after-tax dollars and losing potential market returns on the borrowed amount.

How 401k Loan Interest Rates Are Determined

Unlike personal loans or credit cards where rates depend on your credit score, 401k loan rates follow a specific formula set by your plan administrator.

The Standard Formula: Prime Rate + 1-2%

Most 401k plans set their loan interest rate as the Wall Street Journal Prime Rate plus 1% to 2%. The prime rate is influenced by the Federal Reserve’s federal funds rate, so it changes over time.

Historical Prime Rate Context

PeriodPrime RateTypical 401k Rate (+1%)
2020-20213.25%4.25%
20227.00%8.00%
2023-20248.50%9.50%
Early 20257.50-8.00%8.50-9.00%

Your plan may have a fixed rate or adjust periodically. Check your plan documents for the exact rate.

Who Gets the Interest? (You Do!)

Here’s the key distinction: you pay the interest to your own 401k account. Unlike a bank loan where interest is profit for the lender, 401k loan interest goes back into your retirement savings.

This is why some people describe 401k loans as “paying yourself.” But there are important caveats:

  1. The interest is paid with after-tax dollars — and will be taxed again when you withdraw in retirement
  2. You’re earning interest on your own money — if the money had stayed invested, it might have earned more from market returns
  3. The interest doesn’t replace market gains — your account balance is still reduced by the loan amount

For the full breakdown of this trade-off, see our 401k loan opportunity cost guide.

Current 401k Loan Interest Rates vs Alternatives

How do 401k loan rates compare to other borrowing options in 2025?

Borrowing OptionTypical RateCredit CheckCollateralTax Impact
401k Loan8.5-9.5%NoneYour 401kDouble taxation on interest
Personal Loan7-36%YesNoneNone
Credit Card20-29%YesNoneNone
HELOC8-10%YesYour homeInterest may be deductible
Home Equity Loan7-9%YesYour homeInterest may be deductible

For detailed comparisons, check our 401k loan vs personal loan and 401k loan vs HELOC guides.

How Much Interest Will You Pay?

$30,000 Loan at 8.5% Over 5 Years

  • Monthly payment: $616
  • Total payments: $36,940
  • Total interest: $6,940
  • Interest paid to yourself: Yes, but with after-tax dollars

Effective After-Tax Interest Cost

If you’re in the 22% tax bracket, the interest you pay is effectively more expensive because it’s paid with after-tax dollars:

  • Nominal interest paid: $6,940
  • Pre-tax equivalent: $6,940 ÷ (1 - 0.22) = $8,897
  • Then taxed again in retirement: $6,940 × 0.22 = $1,527 additional tax
  • True cost of interest: Approximately $8,467

This “double taxation” on the interest portion makes 401k loans somewhat more expensive than the stated rate suggests. Learn more about the tax mechanics in our 401k withdrawal tax impact guide.

Can You Negotiate a Lower Rate?

Generally, no. 401k loan rates are set by your plan administrator and apply uniformly to all participants. You can’t shop around or negotiate because the rate is tied to a published benchmark (prime rate).

However, you can:

  • Check if your plan offers a fixed rate option
  • Compare the rate to your other borrowing options
  • Consider a shorter loan term to reduce total interest

Interest Rate and Repayment Schedule

The interest rate directly affects your repayment schedule. Here’s how different rates change the cost of a $25,000 loan over 5 years:

RateMonthly PaymentTotal InterestTotal Paid
5.0%$472$3,307$28,307
6.5%$489$4,367$29,367
8.5%$513$5,783$30,783
10.0%$531$6,873$31,873

For a complete repayment breakdown, visit our 401k loan repayment schedule guide.

Key Takeaways

  • 401k loan interest rates are typically prime rate + 1-2%, currently around 8.5-9.5%
  • You pay interest to your own account, but with after-tax dollars (creating double taxation)
  • The effective cost is higher than the stated rate due to the double taxation effect
  • Rates are set by your plan and cannot be negotiated
  • Compare the 401k loan rate to personal loans, HELOCs, and other options before deciding
  • Shorter loan terms reduce total interest paid

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