Extra mortgage payment calculator
See how an added monthly principal payment may change your mortgage payoff date and interest cost.
New Payoff Time
0 monthsWhat it does
The calculator estimates the regular principal and interest payment, then adds your extra monthly principal payment. It compares the new payoff time and interest cost with the base loan.
Use it to test a repeatable extra amount before changing your mortgage payment strategy.
How to use it
Enter the current loan balance, interest rate, remaining term, and extra payment amount. The result shows the estimated new payoff time and interest saved.
Try adding $100 or $250 using the quick scenarios. A small monthly extra can have a meaningful effect when it is applied consistently.
Common mistake
If a servicer applies extra money to future payments instead of principal, the interest savings can be much smaller. Use the payment memo or servicer instructions required for principal-only payments.
How it works
Mortgage interest is based on the remaining principal balance. When an extra payment is applied to principal, the balance falls faster, so less interest is charged in future months.
The effect can compound over the life of the loan. An extra payment made early usually saves more interest than the same extra payment made near the end, because it reduces the balance for more months.
What affects it
The loan balance, interest rate, remaining term, and extra payment amount drive most of the result. A higher rate or longer remaining term can make extra principal payments more powerful.
Servicer rules also matter. Some lenders let you add principal easily online, while others require special instructions. Prepayment penalties are less common than they used to be, but they are still worth checking.
FAQ
Should I pay extra monthly or once per year? Monthly extras usually reduce principal sooner, but either can help if applied correctly.
Does this lower my required payment? Usually no. Extra principal can shorten payoff time, but the scheduled payment often stays the same unless the loan is recast or refinanced.
Should I invest instead? That depends on rate, risk tolerance, liquidity needs, taxes, and other goals.