Loan payment calculator

How the loan calculation works

This is a level-payment, fully amortizing installment-loan schedule. You can supply either a remaining number of payments or a scheduled payment. When you enter the term, the calculator solves for the level payment. When you enter the payment, it applies that amount until the balance reaches zero and reports the resulting number of payments.

Equal monthly periods

The default method follows equal monthly unit-period arithmetic: the periodic rate is the nominal annual interest rate divided by 12. For principal P, monthly rate r, and n payments, the scheduled payment is P × r ÷ (1 − (1 + r)⁻ⁿ). At a 0% rate, principal is divided evenly across the selected number of payments. This is consistent with the actuarial treatment of regular monthly transactions in Regulation Z, Appendix J.

Daily simple interest — ACT/365 Fixed

The daily method counts the actual calendar days from the interest start date to the first payment and between later scheduled payment dates. Interest for a period is opening balance × nominal annual rate × actual days ÷ 365. Later payments recur on the first payment’s calendar day; a month-end first payment creates a month-end sequence. No weekend or holiday adjustment is made.

Daily and monthly balance methods both exist for simple-interest auto loans, and payment timing can change interest under a daily method, as the Consumer Financial Protection Bureau explains. ACT/365 Fixed is one specific day-count convention; select it only when it matches the agreement you are modeling.

Payment allocation and extra principal

Each scheduled payment covers accrued interest first; the remainder reduces principal. The one-time extra is applied before payment 1, and recurring extra principal is applied after each scheduled payment. Neither extra payment recasts the scheduled payment. The final payment is capped at the amount still due, and the schedule stops when the balance reaches zero.

Interest rate, not APR

The input is an annual interest rate. It is not labeled annual percentage rate (APR), because this calculator does not include origination charges or other finance charges that may be part of a disclosed APR. Enter the rate used to accrue interest on your loan balance.

What is not included

Product-specific fees, origination charges, insurance, taxes, late charges, prepayment penalties, variable rates, skipped payments, business-day adjustments, and lender-specific payment-allocation rules are excluded. Precomputed-interest and add-on-interest loans are not represented by either selectable method. If any applies, use the loan agreement or lender statement as the authoritative schedule.

Internal precision and displayed amounts

The calculation keeps full numeric precision through the schedule and rounds only for display. This avoids creating a residual balance by repeatedly rounding each payment to cents. Displayed rows may therefore differ by a cent from a lender that applies a different contractual rounding policy.