See what adding a little extra to your monthly mortgage payment really does to your timeline and your interest bill. Enter your current balance, the annual interest rate, your regular monthly payment and any extra amount you plan to add each month, and this calculator steps through the loan month by month to find how long until it is paid off and the total interest you will pay. It then compares that against paying with no extra, so you can see exactly how many months you cut off and how much interest you save. Even a modest extra payment can shave years off a mortgage because it attacks the principal directly. Try different extra amounts to find a plan you can stick to. Everything runs locally in your browser.