Lenders and dealers talk in monthly payments because that is the number that feels real. The number that actually decides what a loan costs you is total interest, and it moves in ways the payment hides.
How is a loan payment calculated?
A fixed-rate loan uses the standard amortization formula. Each month, part of the payment covers interest on the remaining balance and the rest reduces the balance. Early on, more of each payment is interest; near the end, almost all of it is principal.
The examples below treat the annual rate as a nominal rate compounded monthly, which closely matches an auto-loan APR when no fees are financed. If fees are rolled into the loan, the APR will be a little higher than the note rate. Do not add fees twice.
Same loan, same rate, four different terms
$25,000 financed at 9.9%:
| Term | Monthly payment | Total interest | Total repaid |
|---|---|---|---|
| 48 months | $632.86 | $5,377.50 | $30,377.50 |
| 60 months | $529.95 | $6,796.81 | $31,796.81 |
| 72 months | $461.89 | $8,255.81 | $33,255.81 |
| 84 months | $413.74 | $9,754.08 | $34,754.08 |
Moving from 48 to 84 months cuts the payment by $219.13, which is why it is offered. It also adds $4,376.57 in interest, and it means you owe more than the vehicle is worth for longer.
Same loan, same term, two different rates
$25,000 over 60 months:
| Rate | Monthly payment | Total interest | Total repaid |
|---|---|---|---|
| 6.9% | $493.85 | $4,631.08 | $29,631.08 |
| 13.9% | $580.41 | $9,824.66 | $34,824.66 |
The rate difference here is $86.56 a month and $5,193.58 in total interest. That is the reason the state of your credit reports matters before you apply, and also the reason nobody can promise you the lower number: lenders set rates, and credit is only one of the things they weigh.
Three questions to ask before you sign
- What is the total amount I will repay? If the answer is only a monthly figure, multiply it by the number of months yourself.
- What is the APR, and what fees are included in it? Compare APR to APR, not note rate to APR.
- What happens if I pay it off early? Most auto loans allow it without penalty, but check.
Try your own numbers in the rate comparison on our home page. It uses the same formula as the tables above and never asks for your contact details.
Sources and review
General consumer information reviewed September 9, 2026 against the sources above. Not legal or financial advice. Loan figures are illustrative calculations, not quotes.