What Is a Mortgage?
A mortgage is a loan specifically used to purchase real estate. The home itself serves as collateral, meaning if you stop making payments, the lender has the legal right to take ownership of the property through a process called foreclosure. In exchange for lending you a large sum of money, the lender charges interest — essentially the cost of borrowing.
Most mortgages in the United States are structured as fully amortizing loans, meaning each monthly payment covers both the interest owed for that month and a portion of the principal (the original amount borrowed). Over time, the interest portion shrinks and the principal portion grows — until the loan is completely paid off.
How Is Your Monthly Payment Calculated?
Your principal and interest payment is determined by three factors: the loan amount, the interest rate, and the loan term. Lenders use a standard amortization formula to calculate a fixed monthly payment that will pay off your loan exactly at the end of the term.
For example, a $320,000 loan (the amount after a 20% down payment on a $400,000 home) at 6.75% for 30 years results in a monthly principal and interest payment of approximately $2,076. Over the full 30-year term, you would pay around $747,000 in total — meaning roughly $427,000 of that is interest. This is why interest rate shopping is so important.
On top of principal and interest, most homeowners also pay:
- Property taxes — collected monthly and held in escrow by your lender, then paid to your local government annually. Rates vary widely by location, typically ranging from 0.5% to 2.5% of the home's assessed value per year.
- Homeowners insurance — required by virtually all lenders to protect the property against damage. Average annual premiums range from $1,000 to $2,500 depending on location and coverage.
- PMI (Private Mortgage Insurance) — required when your down payment is less than 20%. PMI protects the lender, not you, and typically costs 0.5%–1.5% of the loan amount annually.
Fixed-Rate vs. Adjustable-Rate Mortgages
The two main types of mortgages are fixed-rate and adjustable-rate (ARM). With a fixed-rate mortgage, your interest rate stays the same for the entire life of the loan. Your principal and interest payment never changes, making budgeting straightforward and predictable. Fixed-rate mortgages are by far the most popular choice in the United States, particularly for buyers who plan to stay in their home long-term.
An adjustable-rate mortgage (ARM) starts with a fixed rate for an initial period — typically 5, 7, or 10 years — and then adjusts periodically based on a market index. ARMs often start with a lower rate than fixed mortgages, which can be advantageous if you plan to sell or refinance before the adjustment period begins. However, they carry the risk of significantly higher payments if rates rise.
The 15-Year vs. 30-Year Decision
Choosing between a 15-year and 30-year mortgage is one of the most impactful decisions you'll make. Here's what the numbers look like on a $320,000 loan at current rates:
- 30-year at 6.75%: ~$2,076/month — Total paid: ~$747,000
- 15-year at 6.25%: ~$2,744/month — Total paid: ~$494,000
The 15-year loan costs about $668 more per month but saves roughly $253,000 in interest over the life of the loan. You also build equity much faster. However, the higher required payment leaves less cash flow for other investments, emergencies, or life expenses. The right choice depends on your income stability, other financial goals, and how long you plan to stay in the home.
How Your Credit Score Affects Your Rate
Your credit score is one of the most important factors lenders consider. It directly influences the interest rate you're offered, which has a massive impact on your total cost of borrowing. Here's a general guide to how credit scores affect mortgage rates:
- 760–850 (Excellent): Best available rates — you'll qualify for the lowest advertised rates
- 700–759 (Good): Slightly higher rates, but still very competitive
- 640–699 (Fair): Noticeably higher rates — consider improving your score before applying
- 580–639 (Poor): Limited to FHA loans with higher rates and required mortgage insurance
Even a 0.5% difference in interest rate on a $350,000 loan adds up to over $35,000 in extra interest over 30 years. If your credit score is below 700, taking 6–12 months to pay down debt and correct errors on your credit report before applying for a mortgage can save you an enormous amount of money.
How Much Down Payment Do You Need?
The down payment is the portion of the home's purchase price you pay upfront. The remaining amount becomes your loan. While 20% down is the traditional standard, many loan programs allow much less:
- Conventional loans: As low as 3% down (PMI required until you reach 20% equity)
- FHA loans: 3.5% down with a credit score of 580+
- VA loans: 0% down for eligible veterans and active-duty military
- USDA loans: 0% down for eligible rural and suburban home buyers
A larger down payment reduces your loan amount, eliminates or reduces PMI, and often qualifies you for a lower interest rate. If you can put 20% down, you'll save money every single month and over the life of the loan.
Tips for Getting the Best Mortgage Rate
Getting a lower interest rate is the single most powerful way to reduce your total cost of homeownership. Here are the most effective strategies:
- Shop multiple lenders. Rates vary significantly between banks, credit unions, and mortgage brokers. Getting quotes from at least 3–5 lenders can save you 0.25%–0.5% or more.
- Improve your credit score. Pay down revolving debt, avoid new credit applications, and check your report for errors before applying.
- Buy mortgage points. You can pay upfront "points" (1 point = 1% of the loan amount) to permanently lower your rate. This makes sense if you plan to stay in the home long enough to recoup the upfront cost.
- Lock your rate. Once you find a good rate, lock it in writing. Rates can change daily, and a rate lock protects you for 30–60 days while your loan processes.
- Consider the loan type. A 15-year mortgage, VA loan, or USDA loan may offer significantly lower rates than a standard 30-year conventional loan depending on your situation.
What Is Refinancing?
Refinancing means replacing your existing mortgage with a new one — usually to get a lower interest rate, reduce your monthly payment, change your loan term, or tap into your home equity. If rates drop significantly after you purchase your home, refinancing can save you hundreds of dollars per month.
The general rule of thumb is that refinancing makes sense if you can lower your rate by at least 0.75%–1% and you plan to stay in the home long enough to recoup the closing costs (typically $2,000–$5,000). Use our calculator to compare your current payment against what a new rate would cost you.
Understanding Closing Costs
Beyond the down payment, buyers also need to budget for closing costs — fees paid at the time of purchase to finalize the loan. These typically range from 2%–5% of the loan amount and include lender fees, title insurance, appraisal fees, attorney fees, and prepaid items like property taxes and homeowners insurance. On a $400,000 home, expect to pay $8,000–$20,000 in closing costs on top of your down payment.
Some lenders offer "no closing cost" mortgages, but these costs are typically rolled into a slightly higher interest rate — you pay them either way, just over time instead of upfront.