Auto Loan Calculator

Calculate your monthly car payment, total interest, and view a full repayment schedule. Includes sales tax and trade-in value.

This calculator computes Monthly Payment for a car loan built from six inputs: Vehicle Price, Down Payment, Trade-In Value, Sales Tax Rate, Interest Rate, and Loan Term. Trade-In Value works two ways in the Loan Amount formula (lines 11-13): it first reduces the taxable amount that Sales Tax is computed on, then it is subtracted a second time directly from Loan Amount alongside Down Payment — mirroring how many states actually apply a trade-in tax credit. Sales Tax itself is a straightforward product of Vehicle Price (net of trade-in) and Sales Tax Rate, so testing either one 10% low and then 10% high produces an identical 20% total swing in Sales Tax; neither one is the "bigger" driver. At the calculator's own default of $0 Trade-In Value, Vehicle Price dominates Monthly Payment: running it 10% below its default and 10% above it swings Monthly Payment by about 23%, ahead of Loan Term (about 17%) and Interest Rate (about 3% at the default 6.5% rate). That ranking isn't permanent, though — Trade-In Value carries the identical ±1.07 coefficient on Loan Amount that Vehicle Price does (lines 11-13), so it only looks negligible because its default is $0; enter a large trade-in (the field allows up to $200,000) and Trade-In Value's own dollar swing outweighs Vehicle Price's, because the comparison is decided by which input carries the bigger dollar value, not by any inherent "bigger driver" status. Total Interest is led by Vehicle Price too (about 23%) at that same $0 trade-in default, but Interest Rate (about 21%) and Loan Term (about 21%) trail it closely and are essentially tied with each other, since raising either one stretches the same amortization calculation that produces Monthly Payment. Down Payment reduces both Monthly Payment and Total Interest, with a swing of about 3% of each across the same low-to-high test, a smaller effect than Vehicle Price — but not because of any difference in "compounding": both Down Payment and Vehicle Price move Loan Amount along an identical linear path (lines 11-13), with no compounding for either. The gap is scale. Vehicle Price's effect on Loan Amount carries a multiplier of about 1.07 (it also feeds Sales Tax), Down Payment's is exactly -1, and at the defaults Vehicle Price ($35,000) is seven times Down Payment ($5,000) — so a matched ±10% move is a much bigger dollar swing for Vehicle Price. This calculator does not account for dealer fees, registration costs, GAP insurance, or extended warranty add-ons that commonly get rolled into a real auto loan.