Vehicle price + sales tax - down payment - trade-in = financed amount
The shared auto-loan math first estimates the financed amount, then applies the site’s fixed-rate payoff math to project the payment and total interest.
- Start with a vehicle price of $20,000.
- Add sales tax at 4%, then subtract $10,000 down and $0 trade-in value.
- Finance the remaining balance at 4.5% APR over 3 years.
- Compute the resulting payment, interest, and total cost.
Why financed amount matters more than sticker price
Many buyers focus on the monthly payment or the vehicle price alone, but the financed amount is what drives long-term interest cost.
With no trade-in in this example, the full purchase price, plus tax and minus the down payment, is what gets financed.