Reference formulas and worked examples below keep their stated units. Monetary examples use USD; dimensional examples use US customary units unless labeled otherwise. Metric calculator inputs are converted to these reference units before calculation. Choosing another currency does not convert example amounts or exchange money.
How to use this auto loan calculator
Use Payment from vehicle price to compare a car purchase and extra payments. Use Vehicle price from budget to find the most you can finance within a fixed monthly loan budget.
How the calculation works
Amount financed = vehicle price + sales tax + financed fees + trade-in payoff − trade-in value − cash down payment.
Monthly rate r = annual interest rate ÷ 1,200. With financed principal P and n months, the scheduled payment is P × r ÷ [1 − (1 + r)^(−n)]. At 0% interest, it is P ÷ n. A term in years is converted to whole months.
Each month, interest is the opening balance × r, rounded to cents. The scheduled payment and any monthly extra reduce interest first and then principal. A one-time extra reduces the remaining principal in the selected payment month.
Payments are capped at the balance plus interest. The final contractual payment adjusts for any cent-rounding remainder. Extra-payment savings compare the same loan with no voluntary extra payments; a one-time payment after the loan is already repaid has no effect.
Budget mode works backward in whole cents from a zero ending balance using the budget as the monthly loan payment. It finds the largest principal repayable within the term while each payment, including the last, stays at or below the budget. Affordable vehicle price = this principal + cash down payment + trade-in value − trade-in payoff − tax − fees.
Worked example
A $30,000 vehicle with $1,800 tax and $500 financed fees, less $5,000 cash down and no trade-in, finances $27,300. At 6% over 60 months, the regular payment is $527.79. For a separate 0% example, a $400 monthly budget over 60 months supports $24,000 financed; with $5,000 cash down and $2,000 total tax and fees, the vehicle price is $27,000.
Limits and assumptions
Models a fixed-rate, fully amortizing loan with monthly interest and the first payment one month after funding. Daily accrual, irregular dates, variable rates, balloon payments, refinancing, prepayment penalties, and fees not included in principal are excluded. This does not compute APR. Tax is a fixed user-entered amount, not a state tax calculation. Budget mode covers loan payments only; it does not model debt-to-income approval or the other costs of owning a car. Voluntary extra payments are available in vehicle-price mode.
Frequently asked questions
Can I calculate how much car I can afford from a monthly payment?
Yes. Select Vehicle price from monthly budget. The result includes your down payment, trade-in balance, tax, fees, rate, and term. It is a financing scenario, not a lender approval or a complete household affordability assessment.
How does negative trade-in equity work?
Trade-in equity is value minus loan payoff. If payoff exceeds value, the difference increases the amount financed, or reduces the vehicle price supported by a fixed budget.
Does the last payment stay within my budget?
In budget mode, yes. We solve in whole cents with monthly rounded interest, and cap every payment at the budget. The ordinary vehicle-price mode adjusts the final payment to clear a small rounding remainder.
Why do I enter sales tax as a dollar amount?
The taxable base and treatment of trade-ins vary. Enter the applicable estimated tax, and update it when you change the purchase price. The calculator does not silently assume a state rule.
Can I make extra payments or pay cash?
In vehicle-price mode, add a monthly extra and an optional one-time extra to compare payoff time and interest. If cash down and trade-in equity exactly cover the purchase total, the financed amount and loan payments are zero. A zero monthly budget also supports a cash purchase when contributions exceed entered tax, fees, and payoff.
References
CFPB: interest rate, APR, amount financed, and total payments