What does that car really cost monthly?

Price, trade-in, down payment and rate → your real payment, total interest and the interest share of the deal.

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Loan amount
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Monthly payment
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Total interest
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Interest as % of price
How is the car payment calculated?Standard amortization on the financed amount: P&I = L·(r/12)·(1+r/12)^n / ((1+r/12)^n − 1). A $29k loan at 6.9% for 60 months is about $573/mo and ~$5.4k interest.
Is a longer term a trap?60 vs 72 months at the same rate lowers the payment but raises total interest. The tool shows the honest interest number either way — compare total cost, not just the monthly sticker price.
Should I put more down?Every extra dollar down shrinks the financed balance and its interest, and a bigger down payment can also unlock a better rate. Run it with two down-payment amounts to see the difference in total cost.
Negotiate price, not payment?Yes — dealers love steering you to a monthly number. The tool works best when you focus on total interest: that's the number that rewards you for negotiating.