Sources and calculator methodology
Primary consumer guidance, visible assumptions and a clear line between education and an official transaction.
The calculator is original software. These public resources inform the explanatory guides and help readers verify transaction details. Local dealer and state documents remain the source of truth for an individual purchase.
Consumer Financial Protection Bureau — Auto loans
Guidance on shopping for financing, comparing loan terms and understanding the total cost of borrowing.
Open CFPB auto-loan resourcesFederal Trade Commission — Car dealer ads and promotions
Consumer advice on requesting the out-the-door price in writing and checking conditions, fees and add-ons.
Open FTC guidanceFederal Trade Commission — Buying a used car from a dealer
Information on the Buyers Guide, independent inspections, vehicle history and optional add-ons.
Open used-car guidanceUSAGov — State motor vehicle services
A federal directory for locating state registration, title, licensing and motor-vehicle services.
Open state services directoryHow sources are used
Primary sources support general explanations such as why a written total matters, how loan terms should be compared and why optional products need review. The site does not copy official fee schedules into a national database or imply that a static state preset is current everywhere.
Calculation assumptions
Loan results use a monthly fixed-rate amortization formula. OTD calculations apply user-entered tax and fees. The trade and rebate switches control whether those amounts reduce the taxable base in the estimate.