How it works
The standard monthly payment comes from the fixed-rate loan formula, using your balance, monthly rate, and number of payments. Total interest is the standard payment times the number of payments, minus the balance. For the extra payment, the calculator simulates the loan month by month — interest added, then the standard payment plus your extra applied — and counts how many months sooner the balance hits zero and how much interest that avoids. Extra payments only help if your servicer applies them to principal, so check that first.
Frequently asked questions
Do extra payments go to principal automatically?
Not always. Some servicers apply extra money to future payments instead. Ask yours to apply extra payments to principal.
Is it better to pay extra or save?
It depends on your rate versus what savings earn, and whether you have an emergency fund. High-rate debt usually wins; low-rate debt is a closer call.