Mortgage Payoff Calculator
This tool shows the payoff power of adding a little extra to your mortgage each month. It compares your loan on its normal schedule against the same loan with an extra payment, then counts the months and interest you save. Move the sliders to see how even a small extra amount can shorten the loan and cut the total interest.
Adding $200/month pays the loan off 84 months sooner (7.0 years) and saves $103,528 in interest.
Worked examples
Real results from this calculator, computed for a few common scenarios. Move the sliders above to run your own numbers.
| Loan balance = $310,000 | Adding $200/month pays the loan off 103 months sooner (8.6 years) and saves $134,392 in interest. |
| Loan balance = $755,000 | Adding $200/month pays the loan off 0 months sooner (0.0 years) and saves $787,020 in interest. |
| Loan balance = $1,200,000 | Adding $200/month pays the loan off 0 months sooner (0.0 years) and saves $787,020 in interest. |
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How this math works
The calculator runs your mortgage two ways. First it charges monthly interest on the balance and applies your regular payment until the loan is paid off, tracking the months and total interest. Then it does the same with your extra amount added to every payment, where the extra goes straight to principal. Comparing the two gives the months saved and the interest saved.
Extra principal payments are powerful because they cut the balance that all future interest is charged on. Money you add early has the biggest effect, since it removes interest that would have compounded for years. Even a modest extra amount each month can shave years off the loan and save a large sum in interest over time.
Common questions
How does paying extra save so much interest?
Extra money goes directly to principal, lowering the balance that interest is calculated on for every remaining month. Because that reduction compounds over the life of the loan, even small consistent extra payments can produce outsized interest savings.
Does it matter when I start paying extra?
Yes. Extra payments made early have the greatest impact, because they eliminate interest that would otherwise accrue for many years. Starting sooner saves more than the same extra amount started later in the loan.
Will my lender let me pay extra?
Most mortgages allow extra principal payments without penalty, but a few have prepayment penalties, so check your loan terms. Also make sure any extra is applied to principal, not held as a prepayment of your next scheduled payment.
Put this calculator on your website
Bloggers, teachers, credit unions, HR teams: embed the live Mortgage Payoff Calculator free. Copy the snippet below — the tool keeps working and stays up to date automatically, no maintenance on your side.
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