401(k) Loan Repayment Term Calculator

This calculator estimates a level monthly payment for a 401(k) plan loan from the amount borrowed, stated annual rate, and repayment term. Enter the figures shown in your plan documents to see the estimated payment and total paid; plan terms and rules are not modeled.

Formula

The calculator uses the standard fixed-payment loan formula. It treats the annual percentage rate as a nominal annual rate divided into 12 monthly periods.

Monthly payment = round(P × r ÷ [1 − (1 + r)⁻ⁿ], 2)

Total interest = monthly payment × n − P

P is the amount borrowed in dollars; r is the monthly rate, calculated as APR ÷ 1,200; and n is the number of monthly payments, calculated as years × 12. The payment is rounded to cents before the total-interest estimate is calculated.

Worked Example

Using the defaults: P = $20,000, APR = 8%, and term = 5 years.

Monthly rate: 8 ÷ 1,200 = 0.0066667.
Number of payments: 5 × 12 = 60.
Payment before rounding: 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] ≈ $405.53.
Total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

The interest rate remains fixed for the full term.
Payments are level monthly payments made at the end of each monthly period.
Interest compounds monthly at APR divided by 12.
The calculation excludes plan fees, taxes, missed payments, payment changes, and any special plan or employer provisions.

This is estimate arithmetic for education, not financial advice. A 401(k) plan’s loan terms, payment schedule, and consequences of missed or suspended payments depend on its governing documents and applicable rules; this calculator does not determine them. Check the plan’s summary and loan paperwork for the details that apply.

When to Use the Calculator

Use it to translate a proposed loan amount, stated rate, and term into an approximate monthly payment. The inputs should match the figures and payment frequency in the plan paperwork. If your plan quotes a per-paycheck deduction rather than a monthly payment, this result will not directly reproduce that deduction; the number and timing of payroll periods matter.

The term is entered in years, so a term of five years produces 60 monthly payments in this model. If the plan describes a different schedule, the calculator’s monthly-payment result is only a comparison point. Do not assume that the maximum term offered or a particular repayment arrangement applies to you; verify the actual terms with the plan administrator.

How to Read the Results

Monthly payment is the fixed payment implied by the inputs under the formula assumptions. Total interest is the modeled sum of payments minus the amount borrowed. It is not necessarily a complete measure of the economic impact of borrowing from a retirement account: the calculation does not estimate investment performance, plan charges, tax effects, or consequences related to employment changes.

Because each payment is rounded to the nearest cent, small differences can arise if a plan calculates interest daily, uses a different rounding method, or adjusts the final payment. The result may also differ from a paycheck deduction if payments are collected on a schedule other than monthly.

Common Input Mistakes

Using a percentage incorrectly: enter 8 for an 8% APR, not 0.08 or 8.0 as a decimal rate.
Entering the wrong term unit: the term box is in years, not months. Entering 60 means 60 years, not 60 months.
Using a balance instead of the amount borrowed: enter the proposed loan principal, not a retirement account balance or paycheck amount.
Assuming the result includes every charge: plan fees and any nonstandard repayment details are not included.

Limits of This Estimate

This is a general amortization calculation, not a complete 401(k) plan-loan analysis. It does not check whether a loan is available, establish an eligible amount or repayment term, or model plan-specific rules. It also does not calculate the impact of contributions, account investment returns, employment status, tax treatment, or a missed payment. Those details require plan-specific information; consult the plan administrator or the documents for the figures and rules that apply. The result is an estimate, and the plan’s loan disclosure gives the exact figures.

How to Use This List

There is no list of 401 repayment options here: use the calculator by entering the principal, APR, and term from your plan’s paperwork. Change one input at a time to see how the modeled payment responds, then compare the estimate with the plan’s official payment schedule. Treat differences as a prompt to check timing, rounding, and fees rather than as a substitute for the plan’s figures.

Frequently Asked Questions

What does “401(k) loan repayment term” mean?
It is the period over which the plan loan is scheduled to be repaid. The exact term is set out in the applicable plan paperwork.

Does this calculator determine my plan’s maximum term?
No. It calculates payment arithmetic for the term you enter and does not determine plan eligibility, limits, or rules.

Why might my payroll deduction differ from the result?
The calculator assumes monthly payments; payroll deductions may use a different frequency, and plan calculations may include fees or different rounding.

Does the interest estimate include plan fees?
No. The interest output follows the formula and inputs only; fees and other plan-specific charges are excluded.

Can I use this to decide whether to borrow?
No. It is an educational estimate, not financial advice, and it does not evaluate personal circumstances or plan-specific consequences.

Final Thoughts

Use the result as a transparent estimate of level monthly repayment, then confirm the actual schedule and terms in your plan documents.

Formula used

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard loan formula for this calculation, fixed rate and monthly compounding unless stated, rounded as each result states. Not financial advice; no lender, rate or product is recommended. See formulas and assumptions, the disclaimer or report an error.