Mortgage Payoff Calculator — Extra Payments, Time & Interest Saved

This calculator answers one specific question: if you keep the mortgage you already have and simply pay a little extra each month, how much sooner do you finish and how much interest do you escape? That's the whole strategy here — no new loan, no application, no closing costs, no appraisal, nothing to sign. You keep your current rate and your current servicer and just send more than the minimum. It's the cheapest, lowest-friction way to attack a home loan, and it's available to anyone with a few spare dollars in the budget.

Why it works: a fixed-rate mortgage front-loads interest, so in the early years most of your required payment is interest and only a sliver touches the balance. Every extra dollar you add, by contrast, goes 100% to principal. That immediately shrinks the balance that next month's interest is charged on, so the benefit compounds in reverse — which is how even a modest extra can erase years from a 30-year loan.

The tool runs a true month-by-month amortization loop and lays your current schedule beside your with-extra schedule. Each month the interest you owe is interest = balance × (APR ÷ 12); your payment covers that first, and the remainder — plus your extra — knocks down principal: new balance = old balance − (payment + extra − interest). It loops until the balance hits zero, then reports your new payoff date, the months and years you saved, and the total interest avoided.

Worked example. You owe $250,000 at 6% APR with a $1,499 payment. Month-one interest = 250,000 × (0.06 ÷ 12) = $1,250, so only $249 touches principal. Left alone, the loan runs 360 months (30 years) and costs about $289,500 in interest. Add just $200 extra monthly and it clears in roughly 267 months (22 years 3 months) — about 7¾ years sooner — with total interest near $203,300, a saving close to $86,000. Same house, same rate, zero paperwork.

Where people lose the benefit: assuming the extra auto-applies to principal. It often doesn't. Servicers may credit overpayments to next month's bill or stash them in escrow unless you say "apply to principal only" in writing. Confirm it via the online "extra principal" field or a check memo, and glance at your note for a rare prepayment penalty.

One caveat on scope: paying extra never lowers your required monthly payment and never changes your rate — it only shortens the term. If your goal is a smaller monthly bill, or you can drop your rate by 0.5% or more, that's a different decision; run the numbers in our Mortgage Refinance Calculator instead, since refinancing trades closing costs for a new rate. This page is purely about the extra-payment route. Results are estimates — your servicer's rounding, escrow, and exact rate may nudge the final month.