Extra Payment Loan Calculator

About this calculator

Every fixed loan payment splits between interest (balance × periodic rate) and principal, and on an amortizing loan that split shifts toward principal each month as the balance shrinks. Adding a fixed extra amount on top of the required payment goes entirely toward principal, which shrinks the balance faster than the original schedule assumed — and because next month's interest is charged on that smaller balance, the savings compound over the life of the loan.

This calculator re-runs the amortization schedule with your extra payment added each month and compares it against the original schedule to show the total interest saved and the number of months shaved off the term. Mortgage and auto-loan holders, and financial advisors use it to decide whether directing spare cash toward extra principal payments beats other uses of that money, like investing it.