Auto Loan Calculator — payment on what you actually finance

How it works

Two steps. The auto layer: amount financed F = price − down payment − trade-in + taxes & fees. Taxes and fees are entered in dollars rather than as a rate, because vehicle sales-tax rules — including whether a trade-in reduces the taxable amount — differ by state; your purchase order states the actual dollars. The loan: M = F·r(1+r)ⁿ ⁄ ((1+r)ⁿ − 1), where r is the monthly rate (the annual rate divided by 12) and n the number of payments. The term sweep shows the 36/48/60/72-month trade-off on the same amount financed: longer terms shrink the payment and grow the total interest, and the cash-cost output totals what the deal actually consumes — the down payment plus every loan payment.

Worked example

LibreTexts works the loan step at auto scale: a $15,000 loan at 9% over 5 years costs $311.38 a month. The auto layer around it is this page's arithmetic: price a vehicle at $20,000 with $5,000 down and nothing traded in, and $15,000 is what you finance — the same $311.38 payment, about $3,683 of interest over the five years by this calculator's computation. Change any line of the layer — a trade-in, rolled-in fees, a longer term — and the financed amount and payment move with it; only the $311.38 case is a published value (LibreTexts).

Frequently asked questions

Why is the payment computed on the amount financed, not the price?

Because the loan only covers what is left after your down payment and trade-in, plus whatever taxes and fees you roll in. Two buyers of the same car can have very different payments purely from the layer above the loan — which is why this page makes that arithmetic explicit before amortizing.

Does my trade-in reduce the taxes I pay?

In many states a trade-in reduces the taxable amount, in others it does not, and the rules change — which is exactly why this calculator asks for taxes and fees in dollars instead of computing them from a rate. Read the figure off your purchase order or dealer quote and the calculator stays right in every state.

Should the taxes and fees be rolled into the loan?

This page models them as financed — added to the amount borrowed — which is the common dealer default. Paying them in cash instead shrinks the loan: move the dollars from the taxes-and-fees field into the down payment and the comparison is exact.

What term should I look at?

The sweep shows the trade-off rather than picking for you: shorter terms carry higher payments and less total interest, longer terms the reverse. A vehicle also depreciates, so the longer the term, the longer the loan can exceed the car's value — a risk the payment number alone does not show.

What does the cash cost output mean?

The money the deal consumes: your down payment plus every monthly payment over the term. The trade-in is not counted as cash — it is value you surrender — so the cash cost tells you what leaves your accounts, while total interest tells you what the borrowing itself cost.

How is this different from the loan calculator?

The loan calculator compares rate-and-term scenarios on a borrowed amount you already know. This page derives that amount from the vehicle deal — price, down payment, trade-in, taxes and fees — which is the part specific to buying a car; the amortization underneath is identical.

How accurate is this, and what does it exclude?

The financed arithmetic and payment are exact for the dollars you enter. It excludes insurance, registration beyond what you list in fees, manufacturer incentives structured as rate buy-downs, and negative equity rolled over from a prior loan — add that balance to taxes and fees if it applies. Confirm the financed amount against the dealer's purchase order.