A fixed-rate mortgage keeps the same interest rate for the life of the loan, typically a 15- or 30-year term. This keeps your monthly payment for principal and interest steady and predictable over time. Adjustable-rate mortgages, or ARMs, have interest rates that change based on the market, so your payment will go up and down. Most ARMs are based on a 30-year term and typically start with an initial fixed interest rate for a specific period of time, usually 5, 7 or 10 years. It’s important to compare these two types of mortgages to find what’s best for your situation.