Calculate your monthly mortgage payment and see exactly how much time and interest you save with extra principal payments. Add recurring monthly or yearly extras, plus any number of one-time lump sums, and watch your payoff date move up in real time.
Model the effect of paying extra toward principal.
Results
Monthly Payment
$2,023
Loan Amount
$320,000
Total Interest
$408,142
Total Cost
$728,142
More ways to model this loan
This page runs one schedule with one extra-payment plan. The GoFlexi calculator opens up the parts it holds fixed — the extra can change from month to month, the term can carry a balloon or an interest-only opening, and the loan itself can be wrapped and sold on terms.
About This Mortgage Calculator with Extra Payments
This calculator helps homeowners and real estate investors see the true impact of paying down principal faster. Enter your loan details — price, down payment, rate, and term — and the calculator instantly shows your monthly payment, total interest, and full amortization schedule.
Toggle on extra payments to model the effect of paying more toward principal. You can add a recurring monthly extra (for example, rounding your payment up by $200), a yearly extra on any chosen month (common for tax-refund or bonus payments), and one-time lump-sum payments on specific months. Every change recomputes your schedule live: the summary shows how many months you shaved off, how much interest you saved, and your new payoff date, while a balance-over-time chart compares your accelerated payoff to the original schedule side by side.
Whether you're deciding between an extra $100 a month versus one $1,200 payment a year, or simply curious what it would take to pay off your mortgage five years early, this tool gives you a clear, immediate answer. For more advanced scenarios — seller financing, wrap mortgages, balloon payments, and PDF export — check out the GoFlexi calculator. That calculator also lets you type extra payments directly into any row of the amortization table and see the schedule, payoff date, and interest savings update instantly.
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Frequently Asked Questions
How much do extra mortgage payments save?
More than most people expect, because every extra dollar of principal stops accruing interest for the rest of the loan. Take the calculator's default: a $320,000 loan at 6.5% over 30 years has a $2,022.62 payment and $408,142 of total interest. Add $200 a month and the loan pays off in 281 months instead of 360 (6 years and 7 months sooner), and total interest falls by about $105,400. The higher the rate, the more each extra dollar saves. Change the numbers above to see the result for your own loan.
Is it better to pay extra on principal monthly or yearly?
It depends on when in the year the lump sum lands. On the default $320,000 loan at 6.5%, an extra $200 a month saves about $105,400 in interest and pays off in 281 months. The same $2,400 paid once a year saves about $109,300 (278 months) if it's paid at the start of each loan year, the calculator's default timing. Paid at the end of each year instead, it saves about $101,600 (283 months). The rule underneath is simple: the sooner a dollar of principal is gone, the more interest it avoids. Monthly extras land in the middle of those two. The yearly option above lets you pick the month, so enter the month you'd actually pay, such as when a bonus or tax refund arrives.
Does paying extra on a mortgage reduce the term or the payment?
On a standard fixed-rate mortgage, extra principal shortens the term. The required monthly payment stays the same, and the loan ends earlier because the balance falls faster. To lower the payment instead, you ask the lender to recast the loan: you make a lump-sum principal payment and the lender re-amortizes the lower balance over the remaining term. Recasts are usually cheaper than a refinance and keep your rate, but lenders set their own rules. A minimum lump sum and a flat fee are common, and many government-backed loans (FHA, VA, USDA) can't be recast at all. Ask your servicer before you count on it.
How is a monthly mortgage payment calculated?
With the standard amortization formula: payment = P × r ÷ (1 − (1 + r)^−n), where P is the loan amount, r is the annual rate divided by 12, and n is the number of monthly payments. For a $320,000 loan at 6.5% over 30 years, r = 0.065 ÷ 12 ≈ 0.005417 and n = 360, which gives $2,022.62 a month. That payment is fixed for the life of the loan and covers principal and interest only. When you add extra principal, the calculator applies each month's interest to the new, lower balance, which is where the savings come from.
What is included in a mortgage payment?
Principal and interest, plus, for most borrowers, an escrow amount for property taxes and homeowner's insurance. Together these are called PITI. Put less than 20% down on a conventional loan and private mortgage insurance (PMI) is usually added until you reach 20% equity. HOA dues are paid separately but count toward what a lender considers your housing cost. This calculator shows principal and interest only, because that's the part extra payments change. Taxes, insurance, and PMI don't shrink when you pay down principal faster, except that PMI can come off sooner.
How does the interest rate affect my monthly payment?
More than the size of the change suggests, because the rate applies to the whole balance for decades. On a $320,000, 30-year loan, going from 6.5% to 7% raises the payment from $2,022.62 to $2,128.97, about $106 a month. Over the full term that adds about $38,300 of interest. The same effect works in your favor when you prepay: the higher your rate, the more interest each extra dollar of principal avoids.
What is the difference between a 15-year and 30-year mortgage?
A 15-year loan has a higher payment, usually a lower rate, and far less total interest. On $320,000, a 15-year loan at 5.75% costs $2,657 a month and about $158,300 in interest. A 30-year loan at 6.5% costs $2,023 a month and about $408,100 in interest. There's a middle path: take the 30-year loan and voluntarily pay the 15-year amount. At 6.5%, a $2,657 payment retires the 30-year loan in about 16 years with roughly $199,600 of interest. That's about $41,000 more than the real 15-year loan, because you're paying the higher 30-year rate. In return, your required payment stays $2,023 in a tight month. Investors often take that trade for the flexibility.
Is there a penalty for paying off a mortgage early?
Usually not on a home loan, but check your note. Under federal rules (12 CFR 1026.43(g)), a consumer home loan can carry a prepayment penalty only if it is a qualified mortgage, its rate can't go up after closing, and it isn't a higher-priced loan. Even then, the penalty can only apply in the first three years and is capped at 2% of the prepaid balance in years one and two and 1% in year three. Rental-property loans are different. Federal lending rules treat credit to buy or maintain a non-owner-occupied rental as business-purpose credit, so these limits don't apply. DSCR loans commonly carry step-down penalties, such as 5%, 4%, 3%, 2%, then 1% of the balance over five years, or 3%, 2%, 1% over three. On those loans, a large early payoff can cost more than it saves. Your closing disclosure states whether your loan has a penalty and how it's calculated.
What is amortization?
Amortization is how a fixed payment is split between interest and principal over the life of a loan. Each month's interest is charged on the balance still owed, so early payments are mostly interest. On a $320,000 loan at 6.5%, the first $2,022.62 payment is $1,733.33 of interest and only $289.28 of principal. Principal doesn't make up the larger share of the payment until month 233, more than 19 years in. That's why extra payments in the early years do the most good: each dollar removes principal that would otherwise have been charged interest for decades.
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