Many factors impact the cost of owning a home, such as your mortgage principal, property tax bill, homeowners insurance premium, and — this is a big one — your mortgage interest rate. When you understand how your mortgage rate is determined, you can better prepare yourself to buy or refinance a home. Learn more: How mortgage interest works In this article: What is a mortgage interest rate, and why does it matter? Your mortgage interest rate is the price your mortgage lender charges to issue your home l ...