How the monthly payment is calculated
Auto loans use standard amortization: a fixed monthly payment where the split between principal and interest changes over time. Early payments are mostly interest; later payments are mostly principal, even though the total payment stays the same each month.
Where P is the amount financed (price minus down payment), r is the monthly interest rate (annual rate ÷ 12), and n is the loan term in months.
Why the down payment matters
Every dollar of down payment is a dollar you don't have to borrow — it directly reduces the financed amount, which lowers both the monthly payment and the total interest paid over the loan's life, since interest is calculated on the remaining balance.
Reading the amortization chart
The chart breaks down each year of the loan into principal paid (gray) and interest paid (orange). Notice how the orange portion is largest in the early years and shrinks over time — that's the amortization effect: your balance decreases, so less interest accrues on it each month.
Common uses
- Budgeting: checking whether a monthly payment fits your budget before visiting a dealership.
- Comparing offers: seeing how a different term or rate changes total interest paid.
- Down payment planning: deciding how much to put down to hit a target monthly payment.
Frequently asked questions
Does this include taxes, fees or insurance?
No — it calculates the loan payment on the financed amount only. Sales tax, registration fees and insurance vary too much by location to include in a generic formula; add them to the vehicle price manually if you want them reflected.
Is APR the same as the interest rate?
APR (annual percentage rate) usually includes some lender fees on top of the base interest rate, so it's a more complete cost figure. This calculator treats the entered rate as the APR for simplicity.