How Mortgage Interest Rates Are Determined

How Mortgage Interest Rates Are Determined and What Affects Yours

You see a headline rate quoted on a mortgage website. Then you apply and get a different number. Your neighbor just closed and got an even different rate on the same day. Mortgage rates are not one-size-fits-all. They are built from layers of factors — some global, some personal. Understanding these layers helps you make better decisions about when to lock and how to get the best rate available to you.

The Big Picture: What Drives Rates Overall

The Federal Reserve. The Fed does not set mortgage rates directly, but it controls the federal funds rate — the rate banks charge each other for overnight lending. When the Fed raises its rate, borrowing costs throughout the economy tend to rise, pushing mortgage rates up. When the Fed cuts, rates tend to fall. But the relationship is indirect and sometimes delayed.

The 10-year Treasury yield. This is the single best predictor of where mortgage rates are headed. Mortgage-backed securities compete with Treasury bonds for investor dollars. When Treasury yields rise, mortgage rates typically follow. Most of the time, 30-year fixed mortgage rates run about 1.5 to 2 percentage points above the 10-year Treasury yield.

Inflation. Inflation erodes the value of fixed-income investments. When inflation rises or is expected to rise, investors demand higher yields on mortgage-backed securities to compensate. That pushes mortgage rates up. When inflation cools, rates tend to follow it down.

Economic conditions. A strong economy with low unemployment and rising wages generally pushes rates higher because demand for borrowing increases and inflation risk rises. A weakening economy or recession tends to push rates down as the Fed cuts rates and investors flee to safer investments like bonds.

Global events. Geopolitical instability, trade disruptions, or financial crises overseas can push investors toward US Treasury bonds (a safe haven), which drives down yields and can lower mortgage rates. Conversely, global economic growth can push rates higher.

What Determines Your Specific Rate

The factors above set the baseline. Your individual rate is then adjusted based on your risk profile. Here is what matters most:

Credit score. This is the single biggest factor in your personal rate. A borrower with a 760+ credit score might get a rate 0.5% to 1% lower than someone with a 660 score on the exact same loan. On a $400,000 mortgage, that difference can mean $100 to $200 more per month and tens of thousands more in interest over the life of the loan.

Loan-to-value ratio (LTV). LTV measures how much you are borrowing relative to the home's value. A 20% down payment gives you an 80% LTV. A 5% down payment gives you 95% LTV. Lower LTV means lower risk for the lender, which translates to a better rate. The biggest rate improvements come when you cross the 80% LTV threshold.

Loan type. Different loan products carry different rates:

• Conforming conventional loans generally have the lowest rates
• FHA loans may have slightly lower base rates but come with mandatory mortgage insurance
• Jumbo loans (above conforming limits) often carry slightly higher rates
• Investment property loans are priced 0.25% to 0.75% higher than primary residence loans
• ARMs may start with lower rates than fixed-rate loans but carry rate adjustment risk

Loan term. A 15-year mortgage typically has a rate 0.5% to 0.75% lower than a 30-year mortgage. The lender's risk is reduced because the loan is paid off faster and the total interest exposure is lower.

Property type. Single-family homes get the best rates. Condos, multi-unit properties (2-4 units), and manufactured homes typically carry rate adjustments of 0.125% to 0.75% higher.

Occupancy. Your primary residence gets the best rate. A second home adds a small premium. An investment property adds a larger one — typically 0.25% to 0.75% above primary residence rates.

Loan-Level Price Adjustments (LLPAs)

Fannie Mae and Freddie Mac use a matrix of loan-level price adjustments that add or subtract from your rate based on combinations of the factors above. These adjustments are standardized and publicly available. A borrower with a 720 credit score and 80% LTV might pay a 0.375% adjustment, while a borrower with a 660 score and 95% LTV could face a 2.75% adjustment.

These adjustments are cumulative. A low credit score combined with a high LTV, a condo, and investment property use can stack into significant rate increases.

How to Get the Best Rate

• Improve your credit score before applying. Even a 20-point improvement can shift you into a better pricing tier.
• Make a larger down payment. Crossing the 80% LTV threshold eliminates PMI and improves your rate.
• Shop multiple lenders. Rates vary by lender. Get at least three quotes on the same day and compare loan estimates side by side.
• Consider paying points. If you plan to keep the loan long-term, buying discount points can reduce your rate and save money over time.
• Lock at the right time. Once you have a rate you are comfortable with, lock it. Trying to time the market is speculation, and rates can move against you quickly.

Rate Lock Basics

A rate lock guarantees your quoted rate for a set period, typically 30 to 60 days. If rates rise during that window, you are protected. If rates fall significantly, some lenders offer a one-time float-down option. Ask about this before you lock.

Longer lock periods (60 to 90 days) may carry slightly higher rates because the lender absorbs more market risk. Lock for the shortest period that covers your expected closing timeline.

Want to understand exactly what rate you qualify for? SOMA analyzes your profile and shows you how each factor affects your pricing. Start at heysoma.ai.