Vehicle EconomicsAuto Loan Total Interest Calculator
How much of your loan is actually interest, and what one more year of term would add.
Why this comes up
Most payment calculators answer "what will I pay per month" and stop there. That number hides the interest, which can be a fifth, a third, or more of everything you'll actually hand over. This engine puts that figure front and center, and shows what stretching the term by another year would add, the comparison a payment-only tool never surfaces.
How we calculated this
We run the standard fixed-rate amortization schedule for your loan amount, APR, and term, then sum the interest column. To show the next-term comparison, we run the same schedule again at 12 additional months and report the difference.
Worked example, using this page's own defaults ($20,000 at 6% APR, 60 months): total interest comes to approximately $3,173, about 13.7% of everything you'll pay. Stretching to 72 months would add real additional interest on top of that. Run the calculator above to see your own numbers.
What this means
- A high interest share is not automatically bad, it's mostly a function of APR and term length, but it's worth seeing plainly before you sign.
- If the interest share feels high, the fastest lever is usually term, not rate: a shorter term cuts total interest more reliably than hoping for a slightly better APR.
- An extra monthly payment attacks this same number directly, see Extra Car Payment Savings for exactly how much a specific extra payment would cut.
Limitations
This is a planning model, not a lender's payoff statement. Daily simple-interest accrual, exact payment timing, and lender-specific rounding can shift the real figure slightly. See Methodology.
Methodology
This engine is built on Vehicle Economics' fixed-rate amortization model: the standard loan-payment formula run out as a full month-by-month schedule. See Methodology for the full detail.