How the payment is calculated
This calculator uses the same amortization formula as a mortgage: your interest rate is converted to a monthly rate, and a level payment is solved for so that it exactly pays off the loan by the end of the term. Every payment is the same size, but the mix inside it shifts over time. Interest is charged on whatever principal is still outstanding, so a fresh loan carries a bigger interest charge per payment than one that is nearly paid off, even though the dollar amount you hand over each month never changes.
How to read the balance chart
The line above shows your remaining balance at the end of each year. It falls slowly at the start of the loan and picks up speed as you go, because less of each payment is being eaten by interest and more of it is chipping away at principal. A shorter term or a lower rate steepens the curve; a longer term flattens it out and stretches more of your total payments toward interest.
A few things to check before you borrow
This is a planning estimate for a standard fixed rate installment loan with no fees, no skipped payments, and no early payoff. Real auto and personal loans often carry origination fees, and some lenders charge a penalty for paying the loan off early, so read the terms closely before you sign. If you are comparing offers, look at the APR rather than the advertised rate, since APR folds in fees and gives you a cleaner side by side comparison.