Variable Rate
A variable rate (also called an adjustable rate) is an interest rate that changes periodically based on a market index, unlike a fixed rate that stays constant. Variable-rate mortgages start with a lower initial rate that adjusts up or down at set intervals. Your monthly payment changes when the rate adjusts, creating uncertainty but also potential savings.
Variable-rate mortgages in the U.S. are most commonly called adjustable-rate mortgages (ARMs). A 5/1 ARM has a fixed rate for 5 years, then adjusts annually. The rate at each adjustment is calculated as: index + margin = new rate, subject to periodic and lifetime caps. SOFR (Secured Overnight Financing Rate) replaced LIBOR as the primary ARM index after 2023.
For example, a 5/1 ARM at 6.0% with a 2/2/5 cap structure means: the rate starts at 6.0%, can increase or decrease by no more than 2% at the first adjustment, can move 2% per year after that, and can never be more than 5% above the initial rate (maximum 11%). If the index + margin at year 5 is 8.5%, the rate only adjusts to 8.0% (capped at initial + 2%).
ARMs are most advantageous when you plan to sell or refinance before the first adjustment. In 2023, borrowers who took 5/1 ARMs in 2018–2019 experienced their first adjustment at historically high rates. Variable-rate HELOCs adjust monthly with the prime rate and are the most immediately responsive variable-rate product.
Key Takeaway
A variable rate (also called an adjustable rate) is an interest rate that changes periodically based on a market index, unlike a fixed rate that stays constant. Variable-rate mortgages start with a lower initial rate that adjusts up or down at set intervals. Your monthly payment changes when the rate adjusts, creating uncertainty but also potential savings.
Related Terms
Frequently Asked Questions
It can be if rates rise significantly after your initial period. However, with rate caps limiting how much rates can increase, the risk is bounded. ARMs can be a smart choice if you plan to move before the first adjustment or if rates are high and expected to fall.
Your loan documents specify periodic and lifetime caps. A common structure is 2/2/5—rates can move 2% at the first adjustment, 2% per year after that, and no more than 5% total above the initial rate over the life of the loan.
Most new ARMs use SOFR (Secured Overnight Financing Rate), which replaced LIBOR after 2023. Older ARMs may still use LIBOR replacements negotiated in transition terms. Check your loan documents for the specific index and margin.
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