Auto Loan Calculator
How it works
The taxable amount is the vehicle price minus the trade-in (never less than zero), and sales tax is charged on that. The loan amount is then the price plus that tax, minus the down payment and the trade-in — both of which reduce what you need to finance, for different reasons: the down payment is cash you put in, and the trade-in is value the dealer credits you instead of cash. That loan amortizes the same way any fixed-rate loan does: M = loanAmount · r · (1+r)ⁿ / ((1+r)ⁿ − 1), or just loanAmount / n at a 0% rate.
Total paid adds up the down payment and every monthly payment — the trade-in is left out of that figure because it was never cash out of your pocket, even though it lowered the loan.
Frequently asked questions
Why does a trade-in reduce the amount sales tax is calculated on?
In most U.S. states, sales tax on a vehicle purchase is charged on the price minus your trade-in's value, not the full sticker price — trading in a car worth $6,000 against a $28,000 purchase means tax is only calculated on $22,000. This varies by state, though: a few tax the full price regardless of any trade-in, so check your own state's rule before relying on the figure here.
What happens if my down payment and trade-in cover the whole price?
That's a genuinely good outcome, not an error to be confused about — it means you don't need a loan at all. This calculator flags it as an error message rather than silently showing a $0 payment, because there is no loan left for the monthly-payment formula to compute; seeing that message means you can pay the vehicle off outright.
How is this different from a generic loan or EMI calculator?
A generic loan calculator only takes a loan amount, rate and term. This one is built around the two things specific to buying a car: a trade-in, which reduces both the amount financed and (in most places) the amount taxed, and a sales tax rate applied to the purchase — neither of which a general-purpose loan calculator models.