How Car Loans Work

A car loan works like any other amortized loan: you borrow a lump sum and repay it in equal monthly instalments made up of principal and interest. But the amount you actually finance is rarely just the sticker price — sales tax, fees, a down payment and a trade-in all move it before interest is ever applied.

What you actually finance

Start with the vehicle price, add sales tax and dealer fees, then subtract your down payment and any trade-in value. What's left is the loan principal. Because interest is charged on that principal, anything that lowers it — a bigger down payment, a valuable trade-in — directly cuts what you pay.

APR and loan term

The APR is your yearly borrowing rate; the term is how many months you spread it over. A longer term lowers the monthly payment but raises total interest — and can leave you 'underwater', owing more than the car is worth. A shorter term costs more each month but far less overall.

Watch the sales tax rules

In many US states, a trade-in reduces the taxable amount — you only pay sales tax on the price difference, not the full sticker. That can be a meaningful saving, and it's why trade-in value and tax are worth modelling together rather than guessing.

How to pay less

• •Put more down — it cuts the principal and the interest on top of it.
• •Choose the shortest term whose payment you can comfortably afford.
• •Shop the APR separately from the car — a credit union pre-approval is a strong bargaining chip.
• •Be wary of long 72–84 month terms; the low payment hides a high total cost.

1. 1Enter the vehicle price, your down payment and any trade-in value.
2. 2Add your local sales tax rate and dealer fees.
3. 3Set the APR you've been quoted and the loan term in months.
4. 4Compare a shorter term against a longer one to see the interest difference.