Some lenders include fees, escrow (tax/insurance), rounding rules, or different interest timing. This tool is a clean estimate.

The interest rate is the percent applied to your remaining principal (usually monthly for this formula). APR — annual percentage rate — is a standardized yearly cost that, for many installment loans, also folds in certain upfront fees such as origination. If two loans show the same interest rate but one charges a 3% origination fee, that loan’s APR will be higher, which is why APR is the better apple-to-apple comparison. On a simple loan with no fees, APR and the interest rate can match. Credit cards usually advertise a purchase APR that is the periodic rate annualized; an annual fee may sit outside that APR. This calculator treats the APR you enter as the rate used in the payment formula, without layering extra fees.

Many auto, personal, and student installment loans let you send extra principal or pay the balance in full at any time, and extra payments reduce future interest because they shrink the balance the rate is applied to. Some contracts still include a prepayment penalty — a flat fee or a set number of months of interest — especially on certain personal loans or older mortgages. The note, not the monthly statement, is the source of truth. If the loan allows extra payments, apply them to principal (not “toward next month’s payment,” which can just skip a due date). This page assumes you make the scheduled payment for the full term.

Lenders use credit scores as a shorthand for how likely you are to repay on time. Higher scores generally mean lower APRs; thin files, recent late payments, high credit utilization, or collections generally mean higher APRs or a decline. The jump is not linear: moving from the mid-600s into the 700s can change the rate more than moving from 760 to 800. Auto lenders also look at new vs. used, term, and loan-to-value; personal lenders look at income and debt-to-income. Checking your own reports for errors and paying revolving balances down before you apply can improve the offers you see, but the score is only one input.

The shortest term whose payment you can pay every month without draining savings is usually the cheapest. Interest accrues on time outstanding, so 36 months costs less than 60, which costs less than 72, all else equal. “Good” still has to survive a job gap or a car repair. A payment that maxes out your budget on a 36-month term can force missed payments — which cost far more than the extra interest on a slightly longer term. Run the same principal and APR at two terms and compare both the monthly payment and total interest, then pick the shorter one that still leaves a cash cushion.