Auto Loan Calculator

The hard part of a car payment is not the amortisation — it is working out what you are actually borrowing. Regulation Z calls that the amount financed, and 12 CFR § 1026.18(b) defines it as the principal increased by other amounts financed that are not finance charges. In this calculator that comes out as: price, plus sales tax, plus title, registration and doc fees, minus your down payment, minus your net trade-in equity. Tax and official fees sit in the principal rather than the interest because § 1026.4(e) excludes itemised taxes and fees paid to public officials from the finance charge — they are money you borrow, not a cost of credit. Only once that figure is settled does the standard level-payment formula run against it. This is the single reason a dealer quote comes in higher than the number people calculate at home. Type $35,000 into a generic loan tool and you have financed the sticker; the dealer financed the sticker plus 6% tax plus $500 of fees, which is $2,600 more principal and roughly $52 a month more on a five-year note. Two inputs deserve care. The first is sales tax, and the function that computes it deliberately never sees your down payment, because a down payment does not reduce sales tax anywhere in the country — tax is assessed on the transaction price, not on the portion you borrow. Putting $20,000 down on a $35,000 car leaves the tax bill identical. The trade-in is different, and it is genuinely a state-by-state divergence rather than a fact to look up: most states tax the price net of the trade-in, some tax the full price. That is why it is a question on the form instead of an assumption in the arithmetic, and the gap is real money — on a $35,000 car with a $10,000 trade at 6%, the credit is worth $600 of tax and about $12 a month. The taxable base floors at zero, so a trade worth more than the car produces no tax rather than a refund. The second is trade-in equity, which is calculated as value minus what you still owe and is allowed to go negative. If your car is worth $4,000 and the old loan has $9,000 outstanding, that $5,000 shortfall does not vanish — it is added to the new principal and financed at the new rate over the new term. The formula subtracts a signed number, so an underwater trade increases the loan instead of reducing it, and the result panel names the figure rather than burying it. That is the surprise most buyers hit: you start the new loan already underwater on a car that begins depreciating the moment you drive it, and a longer term keeps you there longer. Terms up to 120 months are accepted here, above what most lenders sell, because the honest response to 84-month paper is to show what it costs rather than pretend it does not exist. A note on the rate box: it asks for APR, which on most auto loans equals the note rate because dealer fees are taxes and official charges rather than finance charges. Where a lender does add an origination or acquisition fee, the APR calculator shows how much that widens the gap. If you are weighing 0% dealer financing against a cash rebate, run each as a separate result and compare the total of payments — the rebate shrinks the amount financed on every subsequent line, which can beat 0% on a short term and lose to it on a long one. For a plain unsecured loan without tax and title in the mix, the personal loan calculator uses the same underlying engine.