Auto loan payoff calculator

Key takeaway: A car loan's payment is fixed, but the split inside it isn't. Early on, a large slice of each payment goes to interest and shrinks as the balance falls — so extra principal in the loan's first year does far more good than the same dollars in its last.

This calculator is for drivers partway through a car note who want two answers: when the loan actually ends, and whether paying it down early is worth the cash. A car loan is an installment debt — the payment was fixed at signing and the balance only moves one direction — so the real question is whether to let it run its course.

A fixed payment, a moving split

The entire formula, in plain English: divide your APR by twelve for a monthly rate, and each month multiply your remaining balance by it — that's the interest charge. Your payment covers that first; everything left pays down principal. Each month starts with a smaller balance, so interest shrinks and the principal share grows until the balance is gone. Unlike a card balance, this schedule is locked in — improving it means deliberately paying more than the contract demands.

Take the defaults: an $18,000 payoff balance at 6.9% APR and a $420 payment. The monthly rate is 0.575%, so month one charges $103.50 in interest and $316.50 reaches principal. Carried forward, the loan clears in 50 months — just over four years — with $2,725.94 in interest on $20,725.94 paid overall.

Why year one is where the money is

The balance is never higher than right now, so neither is the interest. On the default loan, $1,119.56 of the $2,725.94 in lifetime interest — about 41% — accrues in the first twelve months, less than a quarter of the term. A dollar of principal cleared in month two stops costing interest for four more years; in month forty-five it barely registers.

Adding $50 a month finishes the default loan in 44 months instead of 50 and cuts interest to $2,390.03 — six months sooner, $335.91 kept. Worth doing — though the same $50 against a card balance at triple the rate saves several times as much. If you carry both kinds of debt, the credit card payoff calculator will usually show the card deserves your spare dollars first, and the debt snowball vs. avalanche calculator can sequence the whole list.

Before you send a big check

A few checks before you send a large principal payment or pay off entirely:

Ask how extra money is applied. Some servicers treat an unlabeled overpayment as an early next payment — due date advanced, nothing saved. Mark it "apply to principal."

Check for a prepayment penalty. Most auto loans don't have one, but some contracts do — read the clause titled "prepayment." A penalty only kills the math if it exceeds the interest you'd avoid.

Get a payoff quote, not just your balance. Simple-interest loans accrue interest daily, so the closing amount changes daily. A ten-day payoff quote gives the exact figure including per-diem interest — about $3.40 a day at the start of the default loan ($18,000 × 6.9% ÷ 365).

Know the precomputed exception. A minority of contracts — mostly older or subprime loans — fix total interest at signing, often by the Rule of 78s, so early payoff refunds much less than the math above promises.

Prepay or refinance?

Prepaying shrinks the balance; refinancing shrinks the rate. The average rate on a new 60-month auto loan is currently 7.1% — if you financed well above that — common with dealer financing, or if your credit has improved — refinancing lowers every remaining month's cost without requiring spare cash. At or below the average, a refinance has little to offer and extra principal is the stronger move.

Two cautions. Refinancing resets the clock — a fresh 72-month term on a loan with 30 months left can cost more total interest at a lower rate — so match or shorten your remaining term. And near the end, the interest left may be too small to justify the paperwork.

How we calculate this

The engine builds your full amortization schedule in integer cents, one row per month: interest at one-twelfth of your APR on the open balance, then your payment, then the principal reduction. It runs until the balance hits zero and reads the payoff month, total interest, and total paid straight off that schedule — the same table shown with your results. It assumes a constant APR and on-time payments; daily accrual on a simple-interest loan can drift by a few dollars, but the payoff month tracks closely.

Frequently asked questions

How is my auto loan payoff date calculated?

We simulate the loan month by month: a month of interest is charged on what you still owe, your payment covers it, and the rest reduces principal. The month the balance hits zero is your payoff date — and since the payment is fixed, it only moves if you pay extra, miss payments, or refinance.

Should I use my original loan amount or my current balance?

Enter your current payoff balance — the cost to close the loan today — not the amount you financed at the dealership. Your lender's app or latest statement shows it; for a full payoff, request a ten-day quote, which includes daily interest through your payment date.

Does paying extra each month actually help on a car loan?

Yes — provided the extra money goes to principal and your loan isn't precomputed. Each dollar of principal you remove stops generating interest for the rest of the term, and the effect peaks early in the loan, when the balance and its monthly interest charge are largest.

How do I find out if my loan has a prepayment penalty?

Read the prepayment clause in your contract, or call your lender and ask. Most U.S. auto loans carry no penalty, but some — often longer-term or subprime contracts — do. If yours has one, weigh the fee against the interest you'd actually save.

What is a precomputed-interest auto loan?

It's a loan where total interest is fixed at signing and built into your payments, often allocated by the Rule of 78s. Because the interest is set by contract, early payoff saves far less than daily-interest math suggests — if your paperwork says precomputed or Rule of 78s, this calculator's savings figures won't apply.

Sources

• Federal Reserve, G.19 Consumer Credit report (Federal Reserve G.19 Consumer Credit report, as of 2026-05-01)
• Consumer Financial Protection Bureau, Auto loans