How this calculator works
This calculator finds the amount you actually need to finance after subtracting your down payment and any trade-in value from the vehicle price, then applies the standard fixed-rate amortization formula used for auto loans. Choose a common loan term from 24 to 84 months to see how it changes the monthly payment and the total interest.
A longer term always lowers the monthly payment but increases total interest, because more months means more time for interest to accrue on the outstanding balance. Comparing a few term lengths side by side is the fastest way to see that trade-off for your own numbers.
The formula
Amount financed = vehicle price − down payment − trade-in valueMonthly payment M = P × i ÷ (1 − (1 + i)^−n)i is the monthly interest rate (annual rate ÷ 12) and n is the loan term in months. Total interest is M × n − P; total cost of the vehicle is the price plus that total interest.
Worked example: $30,000 car, $3,000 down, $2,000 trade-in
- Amount financed = 30,000 − 3,000 − 2,000 = $25,000.
- Monthly rate i = 0.06 ÷ 12 = 0.005; term n = 60 months.
- Payment M = 25,000 × 0.005 ÷ (1 − 1.005^−60) = $483.32.
- Total interest = 483.32 × 60 − 25,000 = $3,999.20; total cost of the car = 30,000 + 3,999.20 = $33,999.20.
Frequently asked questions
Should I use the interest rate or the APR?
The interest rate is what the amortization formula needs. APR can include certain loan fees and is meant for comparing offers; for a quick payment estimate the interest rate on the loan contract is the right input.
Does a trade-in save money the same way a down payment does?
Yes, mathematically — both reduce the amount financed dollar for dollar, which lowers both the monthly payment and total interest. The difference is that a trade-in exchanges a car you own instead of cash.
Why does a 72 or 84-month loan cost so much more in interest?
Stretching the same amount financed over more months lowers each payment, but the balance stays higher for longer, so more interest accrues before it is paid down. The total interest paid rises even though the rate does not change.
Does this include sales tax, registration or add-ons?
No — enter the vehicle price you expect to finance. If tax, fees or extended warranties are rolled into the loan, add them to the vehicle price before subtracting your down payment and trade-in.
Can I use this calculator with no down payment or trade-in at all?
Yes — set both the down payment and trade-in value to zero, and the amount financed simply equals the full vehicle price, since amount financed = vehicle price − down payment − trade-in value. The rest of the calculation works exactly the same way from there, applying the standard amortization formula to the full price instead of a reduced balance.