The number the dealer shows you is the wrong one
Showroom negotiations tend to happen in monthly payments, because almost any price can be made to fit a monthly budget by lengthening the term. A $32,000 car at 7.5% is $641 a month over 60 months and $459 over 96 months — the same car, roughly $4,700 more in interest. Negotiate the price first, then the finance.
How trade-ins affect sales tax
In most US states, sales tax is charged on the price after the trade-in allowance is deducted, so a $8,000 trade-in at 7% tax saves $560 in tax on top of the $8,000 itself. A handful of states tax the full price. If yours does, enter zero in the trade-in field and subtract the value from the price instead.
Negative equity
If you still owe money on the car you are trading in, the shortfall gets rolled into the new loan. The "still owed" field adds it back, which is why the amount financed can be higher than the car's price. Rolling negative equity forward is how buyers end up owing significantly more than the vehicle is worth.
Longer terms and depreciation
A new car loses a large share of its value in the first three years, while a 72- or 84-month loan pays the balance down slowly. The two curves cross late, which means you can spend years underwater — unable to sell without writing a cheque. Shorter terms and larger deposits are the only reliable fixes. If you are weighing the finance against paying cash, the loan calculator and savings goal calculator help you compare the two paths.