How Does Mortgage Interest Work?

By Jamie Cattanach · October 16, 2023 · 9 minute read

We’re here to help! First and foremost, SoFi Learn strives to be a beneficial resource to you as you navigate your financial journey. Read more We develop content that covers a variety of financial topics. Sometimes, that content may include information about products, features, or services that SoFi does not provide. We aim to break down complicated concepts, loop you in on the latest trends, and keep you up-to-date on the stuff you can use to help get your money right. Read less

How Does Mortgage Interest Work?

Mortgage interest is, simply put, the money you pay the bank for the service of lending you the amount you need to buy your home. Interest is expressed as a percent of the loan amount. It is usually rolled right into your monthly mortgage payment of the principal and interest.

This means interest can be something of a hidden cost to homebuyers, especially those on the market for the first time. But it’s still an expense that can really add up. That’s why it’s important for buyers to set themselves up for the best (i.e., lowest) mortgage rate possible.

Here’s what you need to know, including:

•   What is mortgage interest?

•   How does mortgage interest work?

•   How are mortgage rates set?

•   How does an adjustable vs. fixed mortgage differ?

•   How can you get the lowest mortgage rate?

First-time homebuyers can
prequalify for a SoFi mortgage loan,
with as little as 3% down.

What Is Mortgage Interest?

When a bank offers a borrower a significant sum of cash to purchase a house, they’re offering a valuable service, one they expect to be paid for. While an origination or processing fee may apply, the main way a bank makes money on offering a mortgage (or any kind of loan, for that matter) is by charging interest.

Interest is generally expressed as an interest rate, or a percentage of the amount of money you borrow. A lower rate means a lower overall loan cost, since you’ll pay less interest over time.

First-time homebuyers often overlook the impact of interest on the total cost of their home purchase, but it can be significant.

•   An example: At a mortgage interest rate of 6%, a buyer could expect to pay $382,599 on a 30-year mortgage loan of $330,000 This equals a total cost of $712,599, most of which would be interest.

As you can see, it pays to find the lowest rate possible! Fortunately, there are some things you can do as a borrower to set yourself up for the lowest rate possible. It is, however, worth noting that many factors affecting interest rates are out of the borrowers’ control.

💡 Quick Tip: When house hunting, don’t forget to lock in your home mortgage loan rate so there are no surprises if your offer is accepted.

How Are Mortgage Rates Set?

Mortgage rates are calculated using a complex set of factors including both the borrower’s financial status and the health of the economy.

While there’s a lot to say about the economy’s impact on mortgage rates, the simplest rule of thumb is this:

•   When the market is doing well, interest rates tend to be higher.

•   When the market is not doing so great, interest rates tend to be lower.

Mortgage rates also tend to increase with increasing inflation.

Many think that mortgage rates are set by the Federal Reserve (otherwise known as the Fed), but this is a misunderstanding. The Fed sets short-term interest rates that banks use between themselves, but this figure does influence the interest rates of consumer loans including mortgages. So if the Fed’s interest rate is high, chances are mortgage interest rates will be pretty high, too.

Personal financial factors that affect mortgage rates include your credit score, the size of your down payment, and whether the house will be your primary residence or a secondary home or investment property. Generally, rates are higher when the loan is a riskier investment for the bank, which can make sense. The greater the danger of default, the more the servicer wants to be sure they get paid.

Types of Mortgage Rates

There are a variety of mortgage offerings available. You may see offers with varying rates for:

•   Loans designed for lower-income earners, such as FHA, USDA, and VA loans

•   Loans of different lengths, such as a 15-year vs. 30-year home loan

•   Jumbo loans, for those borrowing a larger sum of money to finance a home.

However, one of the biggest decisions is which of the two main types of mortgages, fixed-rate and adjustable-rate, you choose.

Fixed Rate vs Adjustable Rate Mortgages

Fixed-rate mortgages, as their name implies, have one fixed interest rate over the entire lifetime of the loan. If you sign a contract for a fixed-rate mortgage at 5.75%, you can expect to pay that same 5.75% interest rate throughout its term.

Adjustable-rate mortgages, on the other hand, adjust the interest rate depending on market factors. They may start with a fixed rate for a certain amount of time, such as five, seven, or even 10 years. Thereafter, your interest rate (and therefore your monthly mortgage payment) will change over time.

These mortgages can be attractive since they often offer lower rates upfront, and they may come with rate caps to protect borrowers from excessive interest rates. It’s worth noting, though, that they can also be harder to predict and budget for in the long run.

💡 Quick Tip: Lowering your monthly payments with a mortgage refinance from SoFi can help you find money to pay down other debt, build your rainy-day fund, or put more into your 401(k).

Why You Have to Pay Interest on Mortgage Loans

As mentioned briefly above, paying interest compensates a lender for extending you a chunk of cash to buy a home and pay it back over time.

Interest can be one of the key ways that banks make money. For instance:

•   A financial institution might pay customers 3% interest on the money they keep on deposit.

•   The bank might then use some of that money to fund home loans on which borrowers might pay 6.75% in interest.

•   The difference between the 6.75% that the bank is earning on loans vs. the 3% it is paying depositors is part of the way a bank profits and stays in business.

How Lenders Calculate Your Mortgage Payments

As you learned above, interest is rolled right into your home mortgage loan payment. But exactly how much of that money is interest? And how much is going toward the mortgage principal (i.e., the borrowed cost of the home itself)?

The answer depends on where in the loan’s term you are: Earlier on in the mortgage, most of your payment will go to interest. Again, this makes sense: The bank wants to make sure they get paid for their services, even if you decide to repay the mortgage early or stop paying the loan entirely.

Even in the beginning, some of your monthly payment will go to principal — along with any taxes or insurance you may also be paying as part of the mortgage.

Eventually, though, the principal will represent the majority of your payment. The moment when this happens is known as the “tipping point” of a loan — and it’s yet another reason to look for the lowest rate possible. The lower your interest rate, the more quickly your tipping point will arrive, which means you’ll grow your home equity more quickly.

How Interest Works for Different Types of Mortgages

You’ve already read about the two main types of interest: fixed-rate vs. adjustable-rate home loans. But how else does interest on a mortgage work?

Here’s one other option to know about: There is also such a thing as an interest-only mortgage, which allows the borrower to pay — you guessed it — only interest for the first three to 10 years of the loan. Interest-only mortgages can be either fixed-rate or adjustable-rate loans, as described above, but all of them carry some risks since monthly payments can rise so sharply after the initial interest-only period.

How to Get a Lower Mortgage Interest Rate

By this point, you’re probably on board with the idea of finding a good mortgage interest rate.

Given the cost of living in states across the United States — and especially in expensive states like California — keeping housing costs as low as possible is a priority.

While it’s not all under a borrower’s control, there are some ways to ensure your interest rate is as low as it can be. Here are some tips to help.

Get Your Finances in Ship Shape

Although there are lots of things you can’t control about your mortgage interest rate, it’s worth it to take advantage of the things you can. That means getting your financial profile into the best possible shape before applying for a mortgage: reviewing and building your credit score, paying down debt ahead of time, amassing a larger down payment, and, if possible, increasing your income. These steps may take some effort up front, but they can really pay off over time.

Shop Around For Lower Interest Rates

While interest rates are relatively consistent across the market, banks do compete with each other to offer the lowest rates possible — and attract more borrowers. That benefits you because it means shopping around, even just a little bit, can be worthwhile. Reducing your rate by even half a percentage point can save you tens of thousands of dollars over a 30-year loan.

Look into Paying Points

While this may not be the right option for everyone, if you can put additional funds down on some home loans, you could get a better rate. A point equals 1% of your mortgage amount, and if you can pay a point, you can usually lower the rate on your mortgage by 0.25% over the life of the loan.

Recommended: Cost of Living in California

How Mortgage Interest Deduction Works

Although it’s not a way to lower the cost of interest, the mortgage interest deduction allows you to deduct the amount of money you pay on mortgage interest from your taxable income — which lowers what you owe to Uncle Sam come April. In general, how the mortgage interest deduction works is for up to $750,000 in home loan debt.

Tips on Mortgage Interest

Here are a couple of additional ways to get the best deal possible on your mortgage rate:

•   Try the online mortgage calculators that are available. Not only can you get a feel for monthly payments in different scenarios, you can also compare different products, such as a 30-year vs. a 15-year home loan.

•   Consider whether a qualified mortgage broker could help you find offers to suit your needs. These professionals can work as an intermediary between prospective homebuyers and lenders to facilitate the process and research a variety of options.

The Takeaway

Mortgage interest is the money a bank charges for the service of providing a home loan, expressed as a percentage of the loan amount. Getting a lower mortgage interest rate is an important way to keep your home — and your life — affordable over the long run.

Looking for an affordable option for a home mortgage loan? SoFi can help: We offer low down payments (as little as 3% - 5%*) with our competitive and flexible home mortgage loans. Plus, applying is extra convenient: It's online, with access to one-on-one help.

SoFi Mortgages: simple, smart, and so affordable.


How is interest calculated on a mortgage?

How does interest work on a mortgage? Prevailing Interest rates are calculated as a percentage that is based on a variety of economic factors. In terms of borrowers doing the math for a specific interest rate on a certain loan, there are online tools to help with that. And while borrowers can’t control the market, they can work ahead of time to ensure their financial profile is in good shape to get the lowest interest rate possible.

How much interest is paid on a 30-year mortgage?

That depends on the rate, among other factors. For example, a 30-year mortgage for $400,000 at a rate of 6.82% and on a house purchased for $425,000 would cost $540,717 in interest. The total payment of principal and interest would be $940,717. However, if that rate were 5.50%, the borrower would spend only $417,703 in interest.

Do you pay mortgage interest monthly?

Yes, you typically pay mortgage interest monthly. Most home loans roll interest right into their monthly payment, though the amount you pay in interest versus principal will change over time.

Photo credit: iStock/Chainarong Prasertthai

*SoFi requires Private Mortgage Insurance (PMI) for conforming home loans with a loan-to-value (LTV) ratio greater than 80%. As little as 3% down payments are for qualifying first-time homebuyers only. 5% minimum applies to other borrowers. Other loan types may require different fees or insurance (e.g., VA funding fee, FHA Mortgage Insurance Premiums, etc.). Loan requirements may vary depending on your down payment amount, and minimum down payment varies by loan type.

SoFi Loan Products
SoFi loans are originated by SoFi Bank, N.A., NMLS #696891 (Member FDIC). For additional product-specific legal and licensing information, see Equal Housing Lender.

SoFi Mortgages
Terms, conditions, and state restrictions apply. Not all products are available in all states. See for more information.

Financial Tips & Strategies: The tips provided on this website are of a general nature and do not take into account your specific objectives, financial situation, and needs. You should always consider their appropriateness given your own circumstances.

Tax Information: This article provides general background information only and is not intended to serve as legal or tax advice or as a substitute for legal counsel. You should consult your own attorney and/or tax advisor if you have a question requiring legal or tax advice.

Disclaimer: Many factors affect your credit scores and the interest rates you may receive. SoFi is not a Credit Repair Organization as defined under federal or state law, including the Credit Repair Organizations Act. SoFi does not provide “credit repair” services or advice or assistance regarding “rebuilding” or “improving” your credit record, credit history, or credit rating. For details, see the FTC’s website .


All your finances.
All in one app.

SoFi QR code, Download now, scan this with your phone’s camera

All your finances.
All in one app.

App Store rating

SoFi iOS App, Download on the App Store
SoFi Android App, Get it on Google Play

TLS 1.2 Encrypted
Equal Housing Lender