Calculate monthly auto loan payments with trade-in value, down payment, and total interest paid with amortization schedule.
This tool computes the fixed monthly payment on a vehicle loan by subtracting your trade-in value and down payment from the vehicle price to find the amount actually financed, then applying the standard amortization formula against your APR and loan term. It also totals the interest paid over the full term and breaks each month into principal and interest in a schedule. The figure people most often misread is the loan amount itself: sales tax, registration, and dealer fees are usually rolled into the amount financed, so the true balance owed can be higher than price minus trade-in and down payment.
A concrete input and expected output from the current implementation.
Input
Vehicle price $30,000, trade-in value $5,000, down payment $2,000, APR 6%, term 60 months
Expected output
Amount financed: $23,000. Monthly payment: about $444.65. Total interest over 60 months: about $3,679.
Trade-in and down payment reduce the $30,000 price to a $23,000 principal; amortizing that at 6% APR over 60 months gives a level payment of about $444.65, and 60 payments total roughly $26,679, of which $3,679 is interest.
The loan principal is the vehicle price minus trade-in value minus down payment. That principal, the annual rate divided by 12 for a monthly rate, and the term in months feed the standard fixed-payment formula M = P*r(1+r)^n / ((1+r)^n - 1), which produces one constant monthly payment for the life of the loan.
Each month's payment splits between interest, computed on the remaining balance at the periodic rate, and principal, which reduces the balance carried into the next month. Summing every month's interest portion gives total interest paid; summing every payment gives the total cost of the loan, both reported alongside the month-by-month schedule.
Only if you add tax into the vehicle price or loan amount before calculating - the tool doesn't look up tax rates by state or county, so include that figure yourself if the loan is financing the tax.
Dealers often roll extras like an extended warranty, GAP insurance, or documentation fees into the financed amount, and some use a slightly different rounding convention - re-run the calculator with the exact financed amount, rate, and term from the contract to match it.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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