What borrowing really costs.
Monthly payment and lifetime interest on any fixed-rate instalment loan — car, personal, or consolidation.
Standard amortisation on a fixed rate and term, the structure nearly all instalment loans use.
| Scheduled payment | $566 |
| Extra payment | $0 |
| Total interest, as scheduled | $5,984 |
| Total interest, with extra | $5,984 |
| Payoff | 5.0 years |
Excludes origination fees, dealer add-ons and gap insurance, all of which raise the effective rate. Compare offers on APR, not monthly payment.
Term length is where lenders hide the cost
Every fixed-rate instalment loan resolves to the same three inputs: amount, rate and term. Change the term and the monthly payment moves in the direction a salesperson wants while the total cost moves the other way. Stretching a car loan from four years to seven can drop the payment by a third and add thousands in interest — and it leaves you owing more than the vehicle is worth for most of the term.
Compare offers on APR rather than on rate or payment. APR folds origination fees and required charges into a single annualised figure, which is the only number that makes two structurally different offers comparable. On auto loans in particular, dealer financing, add-on warranties and gap insurance are frequently bundled into the amount financed, quietly raising what you pay to borrow.
Extra payments are unusually effective on these loans because they hit principal directly. Because interest is charged on the outstanding balance, an extra $50 a month early in the term removes both that principal and every future month of interest it would have carried. The extra-payment field shows how much time and interest a modest addition buys.
For consolidation the test is simple arithmetic: the new APR, including fees, has to be lower than the weighted average of what you are replacing, and the term no longer than what remains. Otherwise a consolidation loan lowers the monthly payment and raises the total.
Common questions
Does a longer term ever make sense?
Only when the payment is otherwise unaffordable and you intend to pay it down early. Confirm the loan has no prepayment penalty before relying on that.
Rate or APR — which should I compare?
APR. It includes fees, so it reflects the real cost of the loan; two loans with the same rate can carry very different APRs.
How much does an extra payment help?
Substantially, and more the earlier you make it. Every extra dollar retires principal and cancels all future interest that dollar would have accrued.
Sources & method
Payments are amortised at the fixed rate and term entered, using the standard annuity formula.
Extra payments are applied to principal each month; the payoff figure shows the shortened term and the interest avoided.
Origination fees and add-on products are excluded — compare competing offers on APR.
The Index
Every calculator is built the same way: real 2026 figures, method printed at the foot of the page.