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A mortgage is a loan used to purchase a home or other real estate. The borrower agrees to repay the lender over a set period of time — typically 15 or 30 years — through regular monthly payments. Each payment covers a portion of the loan's principal (the original amount borrowed) plus interest charged by the lender.
Because the loan is secured by the property itself, mortgage interest rates tend to be lower than other types of borrowing. However, failing to make payments can result in foreclosure, where the lender takes ownership of the property.
Every mortgage payment is made up of two parts: principal and interest. The principal is the original amount you borrowed, while the interest is the lender's charge for letting you use that money.
Each payment covers the interest first, with the remainder going toward reducing the principal. Early in the loan, most of your payment goes to interest because the outstanding balance is large. As you chip away at the principal, the interest portion shrinks and more of each payment goes toward the balance itself.
You can see this shift clearly in the amortization table — the interest column starts high and gradually falls, while the principal column does the opposite.
The standard formula for calculating a fixed-rate monthly mortgage payment is:
Where:
For example, if you borrow $240,000 at a 6.5% annual rate for 30 years:
Amortization is the process of gradually paying off a loan through regular payments over time. Each monthly payment is split between interest and principal, but the ratio shifts as the loan matures.
The interest portion of each payment is calculated as:
And the principal portion is simply:
Credit cards, on the other hand, are not amortized. They are revolving debt where the outstanding balance can be carried month-to-month and the repayment amount can vary. Interest-only loans and balloon loans are also not amortized in the traditional sense.
An amortization schedule is a table that breaks down every payment over the life of the loan. For each period, it shows how much goes to interest, how much goes to principal, and the remaining balance after the payment.
This schedule is a powerful tool for understanding the true cost of your mortgage. It reveals, for instance, that on a 30-year $240,000 loan at 6.5%, you'll pay over $300,000 in interest alone — more than the original loan amount.
Our calculator generates a full amortization schedule so you can see exactly where each dollar goes, month by month. Note that basic amortization schedules do not account for extra payments, but our calculator does — toggle on additional payments to see their impact.
Many borrowers want to pay off their mortgage ahead of schedule to save on interest. Here are the most common strategies:
Extra payments are additional amounts paid on top of your scheduled mortgage payment. They can be made as a one-time lump sum, monthly, or annually. Because extra payments go directly toward reducing the principal, they lower the interest that accumulates in every future period.
The total interest paid over the life of a loan is:
Where B is the remaining balance at each period. Extra payments reduce B faster, which means less interest accumulates going forward. For example, a one-time additional payment of $1,000 toward a $200,000 loan at 5% interest over 30 years can pay off the loan four months early and save $3,420 in interest. Even an extra $6 per month on the same loan saves $2,796 over its lifetime.
Instead of making one monthly payment, you can pay half of your monthly amount every two weeks. Since there are 52 weeks in a year, this results in 26 half-payments — the equivalent of 13 full monthly payments instead of 12.
That extra payment each year goes entirely toward principal, which can shave years off your loan and save thousands in interest — all without a dramatically larger cash outlay each paycheck.
Refinancing means taking out a new loan to replace your existing mortgage, ideally at a lower interest rate or shorter term. For example, refinancing a $200,000 balance from 5% to 4% on a 20-year term would drop the monthly payment by about $108 and save over $25,900 in total interest.
Keep in mind that refinancing typically involves closing costs and fees. Borrowers should weigh these upfront costs against the long-term savings to determine if refinancing makes financial sense.
Some lenders charge a prepayment penalty if the borrower pays off the loan early. From the lender's perspective, a mortgage is a long-term income stream, and early payoff cuts into their expected returns.
Penalties vary — some lenders charge 80% of six months' worth of interest, while others apply a percentage of the outstanding balance. These fees can be substantial, especially early in the loan. However, prepayment penalties have become less common and usually expire after a set period, such as five years. FHA loans, VA loans, and loans from federally chartered credit unions prohibit prepayment penalties entirely.
Always read the fine print or ask your lender directly about prepayment terms before committing to early payoff strategies.
Before putting extra money toward your mortgage, it's worth considering what else that money could do for you. Since mortgages typically carry relatively low interest rates, the savings from prepayment are modest compared to potential returns from other investments.
For example, if your mortgage rate is 4% but you could earn 10% in a diversified stock portfolio, the math may favor investing instead of prepaying. Similarly, paying off high-interest debt like credit cards — which can charge 20% or more — should generally come first.
Other priorities to consider before accelerating mortgage payments:
Ultimately, whether to pay off your mortgage early depends on your full financial picture — your risk tolerance, other debts, emergency savings, retirement goals, and the peace of mind that comes with owning your home outright.
The down payment is the upfront amount you pay when purchasing a home. It directly reduces the loan amount, which lowers your monthly payment and total interest paid.
A larger down payment means borrowing less, which saves money in the long run. Conventionally, a 20% down payment is recommended because it typically lets you avoid Private Mortgage Insurance (PMI), an extra monthly cost that protects the lender if you default.
Beyond the principal and interest, homeownership comes with recurring costs that can significantly affect your total monthly outlay:
Your true monthly housing cost is the sum of all these expenses:
With a fixed-rate mortgage, your interest rate stays the same for the entire loan term, making your monthly payment predictable. This is the most popular choice for homebuyers who plan to stay in their home long-term.
An adjustable-rate mortgage (ARM) starts with a lower rate for an initial period (commonly 5, 7, or 10 years), then adjusts periodically based on market conditions. ARMs can be attractive if you plan to sell or refinance before the rate adjusts, but they carry the risk of higher payments down the road.
While amortization is most commonly associated with home loans, the concept extends to business accounting as well. Companies use amortization to spread the cost of intangible assets — such as patents, copyrights, trademarks, and goodwill — over their useful life.
Under Section 197 of U.S. tax law, many intangible assets acquired in connection with a business can be amortized over 15 years. This includes customer-based intangibles, licenses, non-compete agreements, and trade names, among others.
Business startup costs can also be amortized under certain conditions, allowing new businesses to deduct qualifying expenses — such as consulting fees, market research, and advertising — over time rather than all at once.