Extra Mortgage Payment Calculator
Making extra payments toward your mortgage principal directly reduces the outstanding balance on which interest is calculated, which means less interest accrues each month going forward. Over time, extra payments can shorten the loan term significantly and save tens of thousands of dollars in total interest. The effect is most powerful when extra payments are made early in the loan term, because the proportion of each payment going toward interest is highest at the start of an amortising mortgage. Extra payments can take several forms: a recurring additional monthly amount added to the regular payment, an annual lump sum (such as a tax refund or bonus), or a single one-time payment at any point during the loan. Most conventional mortgage servicers apply extra principal payments immediately to reduce the outstanding balance, provided you designate the extra amount as a principal payment on your check or online payment. Some servicers apply early payments to future scheduled payments instead, which does not reduce principal early, so it is important to specify the intention. This calculator supports all three forms of extra payment: monthly, annual, and one-time. For each scenario, it shows the new payoff date, the total months saved compared to the original schedule, the total interest saved over the life of the loan, and a year-by-year amortisation comparison between the original and accelerated schedules.
With extra monthly payments of $200, you will pay off your loan in -- months instead of -- months, saving -- in interest.
How extra payments reduce payoff time and interest
The calculator simulates the loan month-by-month. In each month, it applies the standard payment (principal plus interest), then adds any extra payments, and tracks the remaining balance. The loan ends when the balance reaches zero. By comparing the scenario with no extra payments to the scenario with extra payments, we can measure the years saved and interest saved.
month-by-month simulation:
monthly rate = annual rate / 100 / 12
standard payment = PMT(rate, months, loan)
each month: interest = balance x monthly rate
principal = payment - interest
new balance = balance - principal - extra payments
repeat until balance = 0
Worked example
Loan $350,000, rate 6.75%, 30-year term, $200 monthly extra, $2,000 annual extra in December:
- Standard monthly payment (no extras) = approximately $2,330
- Standard payoff = 360 months (30 years)
- Standard total interest = approximately $488,000
-
With $200 monthly extra + $2,000 annual:
Month 1: interest $1,969, principal $361 + $200 extra = $561; balance $349,439
Month 12: same process + $2,000 extra in December - Payoff time = approximately 275 months (23 years), saving 85 months
- Total interest = approximately $375,000, saving $113,000
Year-end balance comparison
Below is a sample of year-end balances for both standard payments and with extra payments:
| Year | Standard balance | With extra balance | Extra principal paid |
|---|---|---|---|
| Calculate above to see balance progression | |||
Strategies for making extra mortgage payments
Extra mortgage payments work best when they are systematic and sustainable. The most effective strategies include: (1) adding a fixed amount to your monthly payment, (2) making a larger payment once per year (e.g., applying a tax refund or bonus), or (3) making occasional lump-sum payments when you receive discretionary income.
For borrowers with inconsistent cash flow, monthly extra payments are ideal because they compound interest savings. For salaried employees with predictable bonuses, an annual payment is convenient. Lump-sum payments are best reserved for truly unexpected windfalls (inheritance, home sale proceeds) rather than required budget items.
The CFPB provides comprehensive guidance on accelerating your mortgage payoff at consumerfinance.gov.
Extra mortgage payment calculator: frequently asked questions
How do extra mortgage payments reduce interest paid?
Extra principal payments reduce the loan balance faster, which means less time for interest to accrue. Interest is calculated as a percentage of the remaining balance each month. The earlier you pay down principal, the less total interest you pay over the life of the loan. For example, paying an extra $200 per month on a 30-year mortgage can save tens of thousands in interest.
What is the difference between principal and interest in my mortgage payment?
Each monthly mortgage payment is split into two parts: principal (which reduces your loan balance) and interest (which compensates the lender). Early in the loan, most of your payment goes to interest. As years pass, the proportion going to principal increases. Extra payments reduce principal faster, which accelerates the shift toward principal-heavy payments and reduces total interest. The CFPB explains mortgage payments at consumerfinance.gov/owning-a-home.
Should I make extra payments or invest the money instead?
The right choice depends on your loan rate, investment returns, and personal circumstances. If your mortgage rate is 6% and you are earning less than 6% in savings or conservative investments, paying down the mortgage is mathematically superior. However, if you have high-interest debt, inadequate emergency savings, or are earning higher returns elsewhere, prioritise those first. The CFPB recommends establishing an emergency fund before aggressively paying down a mortgage.
Can I make extra mortgage payments without penalty?
The vast majority of modern mortgages have no prepayment penalty. However, check your loan documents or ask your servicer to confirm. If you have an older mortgage, FHA loan, or other specialized product, prepayment clauses may exist. Making extra payments is risk-free if no penalty applies, but verify with your lender in writing before making large prepayments.
How often should I make extra payments?
Extra payments can be made monthly (as part of your regular payment), annually (in one lump sum), or whenever you have discretionary funds. Monthly extra payments have a slightly larger impact because they reduce the balance earlier and earn more interest savings. Annual or irregular extra payments still reduce total interest, but by a smaller amount. Automate what you can commit to consistently.
Will extra payments affect my credit score?
No, making extra mortgage payments improves your credit profile. It demonstrates responsible borrowing and reduces your loan balance faster, which can improve your credit utilisation ratio and payment history. This is one of the rare financial actions with purely positive credit consequences. The CFPB provides credit guidance at consumerfinance.gov.
Official sources
- CFPB: What happens if I make extra payments on my mortgage?
- CFPB: Owning a Home resource center.
Reviewed by the CalculatorHub team, edited by James Graham, 13 June 2026. See our methodology. General information, not financial advice.