Project a 401(k) with round-number steppers, then use the sliders above the chart to compare expected return (annual effective) vs loan APR. Taking a loan pulls that cash out of the invested balance — it does not compound until you pay it back. Each monthly repayment (principal and interest from your paycheck) is added back to the 401(k) and then earns the expected return. Year 0 is the starting balance; the gain/loss column is the gap after each year of those payments, not a one-day −$50,000 hole. Turn on Repeat this loan to take another one each time the term ends. Contributions rise 3% a year after year 1.

Runs in the browser. 2026 IRS elective-deferral maximums are $24,500, $32,500 with age-50 catch-up, and $35,750 for ages 60–63. Loan rules vary by plan; the usual IRS §72(p) cap is the lesser of 50% of the vested balance or $50,000 minus the highest outstanding in the prior 12 months.