Mortgage Payoff Calculator
See how extra payments can save you thousands in interest and help you pay off your mortgage years sooner. Adjust the fields below — results update instantly.
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Updated March 2026 · Based on standard amortization formulas
How to Calculate Your Mortgage Payoff
A mortgage payoff calculation compares two scenarios: your current payment plan versus one with extra payments. The math uses the standard amortization formula that banks use to structure your loan.
The amortization formula
- M = monthly payment
- P = principal (remaining balance)
- r = monthly interest rate (annual rate ÷ 12)
- n = total remaining payments
Step-by-step
- Enter your current mortgage balance — check your latest statement or call your servicer for the exact payoff amount.
- Enter your annual interest rate. This is on page 1 of your Closing Disclosure or on your monthly statement.
- Enter your current monthly principal and interest payment (not including taxes, insurance, or PMI).
- Choose how much extra you want to pay each month — even $100 makes a difference over 30 years.
- Optionally add a one-time lump sum (like a tax refund or bonus) applied immediately to principal.
What Affects Your Mortgage Payoff Timeline
Several factors determine how quickly you can pay off your mortgage and how much interest you'll save.
Interest rate
Higher rates mean a larger share of each payment goes to interest. At 6.5%, roughly 60% of your first payment is interest. At 3.5%, it's closer to 40%. Higher rates amplify the savings from extra payments.
Remaining balance
A larger balance generates more monthly interest. On a $400,000 balance at 6.5%, you pay ~$2,167 in interest in the first month alone. Extra payments have the most impact when your balance is highest — early in the loan.
Extra payment amount
Consistency matters more than size. An extra $200/month on a $300,000 loan at 6.5% saves ~$62,000 over the loan. Doubling to $400/month saves ~$100,000 — not exactly double, because of compounding interest reduction.
Payment timing
Earlier payments save more interest because they reduce the principal that compounds over the remaining life of the loan. A $10,000 lump sum in year 1 saves roughly 3× more interest than the same payment in year 15.
Loan term remaining
If you have 25 years left, extra payments compound over a longer period. With only 5 years left, the impact is smaller because you've already paid most of the interest in the early years of the loan.
Pro Tips for Paying Off Your Mortgage Faster
- Use the 1/12 rule. Divide your monthly principal payment by 12 and add that amount to each payment. You'll make the equivalent of 13 payments per year instead of 12.
- Apply windfalls to principal. Tax refunds, work bonuses, and inheritance — direct these to your mortgage principal for the biggest interest savings.
- Always specify "apply to principal." Contact your servicer to ensure extra payments reduce your balance, not pre-pay future months.
- Check for prepayment penalties first. Most modern loans don't have them, but loans from before 2014 or certain ARMs may charge 1-3% of the remaining balance.
- Consider refinancing if rates drop. If current rates are 1%+ below your rate, refinancing to a shorter term (e.g., 15 years) can dramatically reduce total interest — even with closing costs.
Frequently Asked Questions
How much can I save by paying extra on my mortgage?
The savings depend on your balance, interest rate, and how much extra you pay. For example, on a $300,000 mortgage at 6.5% interest, paying an extra $500 per month can save you roughly $87,000 in interest and help you pay off the loan about 8 years sooner. Even an extra $100 per month can save over $30,000 in interest on a 30-year loan. Use our calculator above to see your exact savings based on your loan details.
Is it better to make extra monthly payments or a one-time lump sum?
Both approaches reduce your interest costs, but they work differently. Extra monthly payments provide steady, compounding savings over time and are easier to budget for. A one-time lump sum creates an immediate principal reduction, which reduces interest from that point forward. For maximum impact, combine both strategies — make consistent extra monthly payments and apply windfalls like tax refunds or bonuses as lump-sum payments. Our calculator lets you model both scenarios.
Does my extra mortgage payment go toward principal or interest?
You must specify that extra payments go toward principal, not future payments. Contact your mortgage servicer for instructions — most allow you to designate principal-only payments online or by writing 'apply to principal' on the check. Without this designation, your servicer may apply the extra amount to your next month's payment instead, which does not reduce your total interest cost. Some lenders have a separate online field for additional principal payments.
Is there a penalty for paying off my mortgage early?
Most modern mortgages do not have prepayment penalties, but some loans — especially those originated before 2014 or certain adjustable-rate mortgages — may include one. Prepayment penalties typically apply only in the first 3 to 5 years of the loan and range from 1% to 3% of the remaining balance. Check your original loan documents or Closing Disclosure for a 'Prepayment Penalty' section. If you have one, calculate whether the interest savings from early payoff exceed the penalty cost.
Should I pay off my mortgage early or invest the extra money?
This depends on your mortgage interest rate versus your expected investment returns. If your mortgage rate is 6.5% or higher, paying it off early provides a guaranteed 6.5% return (your avoided interest). If your rate is below 4%, investing in a diversified stock portfolio historically returns 7-10% annually, potentially outpacing your mortgage interest. Consider your risk tolerance, tax situation, and whether you have high-interest debt to pay off first. Many financial advisors recommend a balanced approach — make some extra mortgage payments while also contributing to retirement accounts.
How does the mortgage payoff calculator work?
Our calculator uses the standard amortization formula to compute your monthly interest charges and principal reduction for each payment. It generates two scenarios: your current payoff timeline and a second timeline that includes your extra payments. The formula is M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is principal, r is the monthly interest rate, and n is the total number of payments. The calculator then compares the total interest and payoff dates between both scenarios to show your savings. Results update instantly as you type.
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