The mortgage type you choose affects how predictable your payment feels. A fixed-rate loan is built around stability. An adjustable-rate mortgage, or ARM, is built around an initial fixed period followed by possible rate changes.
How a fixed-rate mortgage works
With a fixed-rate mortgage, the interest rate is set when you take out the loan and does not change during the loan term. Your scheduled principal-and-interest payment stays the same, though taxes, insurance, PMI, and HOA dues can still change the total monthly payment.
Fixed-rate loans can be easier to budget because the core loan payment is predictable. They may fit buyers who expect to stay in the home for a long time or who do not want to rely on refinancing later.
How an adjustable-rate mortgage works
An ARM typically has an introductory period when the rate stays fixed, such as 3, 5, 7, or 10 years. After that period, the rate can adjust based on an index plus a lender-set margin, subject to the loan's caps and rules.
An ARM may start with a lower rate than a fixed-rate loan, but the future payment is less certain. If rates rise, the monthly payment can rise too.
When a fixed-rate loan may fit
- You want predictable principal-and-interest payments.
- You expect to keep the home or loan beyond an ARM's introductory period.
- You would be uncomfortable if the payment increased after an adjustment.
- You are comparing affordability and want fewer moving parts in the estimate.
When an ARM may fit
- You understand the adjustment schedule, caps, index, and margin.
- You can afford the payment if it rises within the loan's allowed limits.
- You expect a shorter holding period, but you are not depending on a sale or refinance to make the loan affordable.
- You have compared the full payment, not just the starting rate.
Questions to ask before choosing
Ask when the rate first adjusts, how often it can change, what the maximum payment could become, what index is used, what margin applies, and whether the loan has limits on increases or decreases. Then compare the starting payment and a higher-rate scenario in the Mortgage Calculator.
Helpful references
- CFPB: Fixed-rate vs adjustable-rate mortgage loans
- CFPB: ARM index and margin
- CFPB: Adjustable-rate mortgages
Compare payment scenarios
Run fixed-rate and ARM assumptions side by side.
Test the monthly payment at the starting rate and at a higher possible rate before choosing a loan type.