A variable interest rate (sometimes called an “adjustable” or a “floating” rate) is an interest rate on a loan or security that fluctuates over time because it is based on an underlying benchmark interest rate or index that changes periodically.

The obvious advantage of a variable interest rate is that if the underlying interest rate or index declines, the borrower’s interest payments also fall. Conversely, if the underlying index rises, interest payments increase. Unlike variable interest rates, fixed interest rates do not fluctuate.