Search results treat “auto loan calculator” and “car payment calculator” as twins. Product-wise, they should not be clones. One job is to amortize a clean financed principal and show the schedule. The other job is to answer “what might I pay monthly after trade-in, tax, and fees?” Keeping those jobs separate prevents thin duplicate pages and clearer decisions.

Start with vehicle price, subtract down payment and trade-in, then amortize the remainder at a fixed rate you enter. The schedule shows how each payment splits into interest and principal and how the balance falls to zero. That view is ideal when you already know the financed amount—or want to ignore tax temporarily to compare terms.

Payment-first buyers care about tax and fees that often get rolled into the loan. A simplified model taxes price minus trade-in, adds fees, subtracts cash down, then computes the payment. It emphasizes the payment and financed breakdown rather than printing every schedule row.

CFPB materials on auto loans and amortization remain the neutral reference for how installment interest works. Use worksheets to organize assumptions; use disclosures to decide.