What is the Payoff vs. Interest Calculator?
This calculator helps you decide whether to pay off a car loan in a single lump-sum payment today or keep making the scheduled monthly payments. It shows exactly how much interest you'd avoid by paying off now, and — if you'd rather use that cash elsewhere — compares it against what the same lump sum could grow to if invested instead.
How does the underlying math work?
The calculator first simulates your loan month by month at the current balance, APR and payment to find how long it would take to reach zero and how much total interest that accrues — the same amortization logic behind the site's Debt Payoff Calculator. Paying off today eliminates every remaining interest charge, so the guaranteed savings equal that projected total interest. For the investment comparison, it grows today's payoff amount at your entered rate, compounded monthly, over the same number of months the loan would otherwise run, then compares the gain to the interest you'd save.
Real-world practical application
This comes up whenever a windfall arrives — a bonus, tax refund, or inheritance — and you're deciding what to do with it. It's also useful for comparing a low-rate auto loan against a higher-rate debt elsewhere (pay off the higher-rate debt first) or against a savings account or investment with a meaningfully higher expected return, where keeping the loan and investing the cash can sometimes come out ahead.
Frequently Asked Questions
Is paying off a car loan early always the right move?
Paying off the loan guarantees you avoid every dollar of remaining interest, which is a certain, risk-free return equal to the loan's APR. It is usually the right move unless you could reliably earn a higher after-tax return elsewhere, or you'd be left without any cash cushion.
What does it mean to be "upside-down" on a car loan?
You're upside-down when the loan balance is higher than the car's current market value. It doesn't change the math on whether to pay off the loan, but it matters if you're considering selling or trading the car in, since you'd owe more than a buyer or dealer would pay for it.
Are there early-payoff penalties on auto loans?
Most modern auto loans don't charge a prepayment penalty, but a small number of older or subprime contracts do. Check your loan agreement for a "prepayment penalty" or "rule of 78s" clause before paying it off in full.
Related Calculators
- Auto Loan Calculator — the true monthly cost of financing a vehicle.
- Debt Payoff Calculator — the same payoff math for a credit-card balance.
- Real ROI Calculator — your true after-tax, after-inflation return on an investment.