Mortgage interest is the cost you pay to borrow money to buy a home. It’s calculated as a percentage of your loan balance and makes up a large portion of your monthly payment—especially in the early years of your mortgage. Over time, as you pay down what you owe, the amount of interest you pay each month gradually decreases.
In this Redfin article, we’ll break down mortgage interest in plain language, including:
- What mortgage interest is and where it shows up in your payment
- How principal, interest, and amortization work together
- Why early payments are interest-heavy
- How to read an amortization schedule to understand long-term costs
Mortgage interest basics: principal, interest, and amortization
When you make a mortgage payment, your money is split between two main components: principal and interest. How those amounts are divided each month is determined by amortization.
Think of it like this:
- Principal – The amount you borrowed to buy the home
- Interest – The fee the lender charges for lending you that money
- Amortization – The schedule that determines how your loan balance is paid down over time through fixed monthly payments
At the start of your loan, a larger share of your payment goes toward interest. As the principal balance shrinks, more of each payment goes toward paying down the loan itself.
Mini amortization example (30-year loan, fixed rate):
| Payment | Total Payment | Interest | Principal | Remaining Balance |
| 1 | $1,500 | $1,200 | $300 | $299,700 |
| 12 | $1,500 | $1,150 | $350 | $295,800 |
| 60 | $1,500 | $1,000 | $500 | $272,000 |
This gradual shift is the core of how mortgage interest works.
What mortgage interest is and how it shows up in your payment
Mortgage interest is essentially the price you pay for access to borrowed money. Lenders charge interest to offset risk and earn a return over the life of the loan.
In a typical monthly mortgage payment, interest appears alongside other housing costs:
Sample monthly payment breakdown:
- Principal: Pays down your…