Fixed-Rate Mortgage vs. Adjustable-Rate Mortgage: How Each Loan Works

A fixed-rate mortgage and an adjustable-rate mortgage (ARM) both let a buyer borrow money to buy a home and pay it back over years. The difference is in the interest rate. With one, the rate stays the same for the life of the loan. With the other, the rate can move up or down after an initial period. That one difference changes how predictable the monthly payment is, and how much risk the borrower takes if rates move.

How a fixed-rate mortgage works

A fixed-rate mortgage keeps the same interest rate from closing until the loan is paid off or refinanced. The part of the payment that covers principal and interest does not change. The total payment can still move if property taxes, homeowners insurance, or mortgage insurance change, because lenders often collect those amounts with the monthly payment.

Common terms are 30 years and 15 years. A 30-year loan spreads payments over a longer period, so each payment is smaller, but the borrower pays interest for more years. A 15-year loan has larger monthly payments and usually a lower rate than a 30-year loan from the same lender, and the balance falls faster. Lenders set the rate at closing based on the borrower’s credit, down payment, loan size, and market rates at that time.

How an adjustable-rate mortgage works

An adjustable-rate mortgage starts with a fixed rate for a set number of years, then adjusts at set intervals. A loan labeled 5/1, for example, keeps its starting rate for five years and then can adjust once a year. A 7/1 loan keeps its starting rate for seven years before yearly adjustments begin, and a 10/1 loan does the same for ten years.

After the initial period, the rate is set by adding a margin set by the lender to a published index. If the index rises, the rate rises. If the index falls, the rate falls. Loan documents set caps that limit how much the rate can rise at the first adjustment, at each later adjustment, and over the life of the loan. The size of those caps differs from loan to loan, so borrowers need to read the loan documents for the exact numbers.

ARMs often start with a lower rate than a fixed-rate loan from the same lender. That lower start can mean a smaller payment in the early years. The trade-off is that the payment can rise later, and a borrower who still holds the loan when rates are higher will pay more.

Fixed-rate mortgage vs. adjustable-rate mortgage

	Fixed-rate mortgage	Adjustable-rate mortgage (ARM)
What it is	A home loan with an interest rate that stays the same for the full term of the loan.	A home loan with an interest rate that is fixed for an initial period and then adjusts at set intervals.
Who qualifies and gets it	Homebuyers who meet a lender’s credit, income, and down payment standards.	Homebuyers who meet the same standards; lenders also check that the borrower could handle a higher payment after an adjustment.
Costs	The starting rate is often higher than an ARM from the same lender, but the principal and interest payment does not change. Total interest depends on the term and the rate set at closing.	The starting rate is often lower, so early payments are often smaller. Payments can rise after adjustment, and refinancing to a new loan carries its own closing costs.
Pros	Predictable principal and interest payment; no payment increase if market rates rise; simple to plan around for a long stay.	Lower starting rate and smaller early payments; can suit a buyer who plans to move or refinance before the first adjustment.
Cons	Higher starting rate than a comparable ARM; if market rates fall, the borrower must refinance to get a lower rate.	Payments can rise after the initial period; the borrower takes the risk that rates will be higher when the loan adjusts.

The verdict: which loan fits which case

Choose a fixed-rate mortgage if you plan to stay in the home for a long time, want the same principal and interest payment each month, have a budget with little room for a higher payment, or do not want to track rate changes or refinance on a deadline.

Choose an adjustable-rate mortgage if you plan to move or refinance before the first adjustment, can handle a higher payment later, and want the lower early payment in exchange for taking on the risk that rates will rise.

Neither loan is better in every case. The better choice depends on how long the borrower plans to stay, how much payment change the household budget can absorb, and what rates lenders are offering when the loan closes. Rate offers change over time, so the comparison should be run again with current quotes before signing.

Explainer based on mortgage guidance published by the Consumer Financial Protection Bureau.