Mortgage Extra Payment Calculator

About this calculator

This calculator builds two amortization schedules side by side: one where you pay only the scheduled principal-and-interest amount, and one where a fixed extra amount goes straight to principal every month. Because mortgage interest is charged on the remaining balance, every extra dollar of principal paid early stops accruing interest for the rest of the loan — which is why even a modest extra payment can cut years off a 30-year term.

Homeowners use this to decide whether to round up a payment, apply a bonus or tax refund, or set up biweekly payments that effectively add one extra payment per year. It's also the standard way loan officers and financial planners illustrate the trade-off between paying down a mortgage faster versus investing the same money elsewhere.