Mortgage Payoff Calculator
See when your mortgage will be paid off, how much total interest you'll pay, and how many years and dollars of interest an extra monthly payment could save you. Everything runs in your browser; nothing is uploaded.
A simplified approximation for planning intuition, not financial advice. Assumes a fixed rate and consistent payments for the life of the loan.
How mortgage payoff works
A mortgage is an amortizing loan, which means every monthly payment is split between interest and principal. Interest is charged on your remaining balance, so at the start of a loan — when the balance is largest — the bulk of each payment goes to interest and only a little chips away at what you owe. As the balance shrinks, the interest portion falls and more of each payment attacks the principal. This is why the early years of a mortgage feel like you are barely making a dent, and why the balance falls faster and faster toward the end.
This calculator amortizes your loan month by month. It applies your interest rate to the current balance, subtracts the interest from your payment, and reduces the balance by whatever principal is left over. It repeats that until the balance reaches zero, which gives you an exact payoff date and the total interest you'll pay over the life of the loan. Because interest compounds on the outstanding balance, the total interest on a 30-year mortgage can rival or even exceed the amount you originally borrowed.
Why extra payments are so powerful
When you add an extra amount to your monthly payment, every dollar of it goes straight to principal — there is no interest due on it yet. Reducing the principal early means the loan accrues less interest for the entire remaining term, and each subsequent payment then knocks out even more principal. The effect snowballs. A modest extra payment can shave years off the loan and save tens of thousands of dollars in interest, because you are attacking the balance during the years when interest charges are highest.
The calculator above shows this directly: it runs your loan twice, once with just the minimum payment and once with your extra payment added, then reports the difference in payoff time and total interest. Try nudging the extra payment up and down to see how sensitive the savings are — you'll often find that even $100 to $200 extra per month has an outsized impact.
Should you pay off your mortgage early?
Paying extra guarantees a return equal to your mortgage rate, which is attractive when rates are high. But it isn't always the best use of a dollar. Consider these trade-offs first:
- Match against other goals. High-interest debt and an employer 401(k) match usually beat extra mortgage payments.
- Keep an emergency fund. Money paid into a mortgage is hard to get back out; don't drain your cash cushion.
- Compare to investing. If your mortgage rate is low, long-run investment returns may exceed the guaranteed savings from prepaying.
- Confirm no prepayment penalty. Most modern mortgages have none, but check your loan terms.
Frequently asked questions
What monthly payment should I enter?
Use your principal-and-interest payment — the part that pays down the loan — not your full bill. Escrow amounts for property taxes and homeowners insurance don't affect the loan payoff, so leave them out for an accurate result.
Why does my payment need to exceed the monthly interest?
If your payment is smaller than the interest that accrues each month, the balance grows instead of shrinking and the loan never pays off. The calculator flags this so you can raise the payment to a level that actually reduces principal.
Is the extra payment applied to principal?
Yes. This tool assumes any extra amount goes entirely toward principal, which is how most lenders apply it — though it's worth confirming your servicer does the same and doesn't just advance your next due date.
Does this include taxes, insurance, or PMI?
No. It models only the loan's principal and interest. Private mortgage insurance typically drops off once you reach about 20% equity, which is a separate saving from paying the loan down faster. Planomy's full app can fold your mortgage into your complete net-worth plan.
Want the full picture?
Planomy projects your entire plan — taxes, retirement accounts, Monte Carlo, and plan-vs-actual tracking — not just one number. It's free, private, and runs right in your browser.