Auto Loan Calculator: How It Works
A car loan is unusual among consumer debts: the thing you borrowed against loses value faster than you repay the balance. That gap — owing more than the car is worth — is the defining risk of vehicle finance, and it drives almost every piece of advice on this page.
Depreciation versus your balance
A new car typically loses 15–25% of its value in the first year and roughly half within three. A loan balance, meanwhile, falls slowly at first because early payments are mostly interest. Plot the two and they cross somewhere in the middle of a long loan — before that point you are in negative equity.
| End of year | Car worth (approx.) | Balance on a 7-yr, 5% loan, 10% down | Position |
|---|---|---|---|
| 1 | 78% | 80% | Negative |
| 2 | 67% | 70% | Negative |
| 3 | 58% | 58% | Break-even |
| 4 | 51% | 46% | Positive |
Percentages are of the original purchase price. If the car is written off or stolen while you are in negative equity, a standard insurance payout covers the car's value, not your debt, and you keep paying for a car you no longer have. This is exactly the gap that GAP insurance is designed to cover, and it is the one add-on that is often worth its price on a long loan with a small deposit.
What actually reduces the cost
- A bigger deposit. It cuts the balance, shortens the negative-equity window and often unlocks a better rate tier.
- A shorter term. Seven- and eight-year car loans exist because they make expensive cars look affordable. They roughly double the interest against a four-year term.
- Financing separately from buying. Arrange a loan with a bank or credit union first, then negotiate the car as a cash buyer. Dealer finance is a profit centre; having an approved rate in hand is your strongest lever.
A worked example
A 25,000 car, 3,000 deposit, 22,000 financed at 6%:
| Term | Monthly | Total interest |
|---|---|---|
| 3 years | 669 | 2,084 |
| 5 years | 425 | 3,520 |
| 7 years | 321 | 5,004 |
The seven-year option saves 348 a month against three years and costs an extra 2,920. It also keeps you in negative equity for roughly three years rather than one.
The 0% finance question
Manufacturer 0% offers are real, but they are usually an alternative to a cash discount rather than in addition to it. If the dealer will take 23,000 cash or 25,000 at 0% over four years, the '0%' loan carries 2,000 of hidden interest — an effective rate of roughly 4.2%. Always ask what the cash price would be, then compare.
Watch the total, not the monthly
Vehicle sales are conducted almost entirely in monthly payments, because any price becomes affordable if the term is long enough. Before you discuss finance, decide the total you are willing to spend on the car. Then check that the finance fits it — not the other way round.
Balloon payments and PCP-style deals
Some agreements keep monthly payments low by deferring a large final payment. You then choose between paying it, refinancing it, or handing the car back. These can suit people who change cars often, but the running total across several cycles is usually higher than owning outright, and mileage limits and condition charges add costs that never appear in the advertised monthly figure.