An interest rate that is allowed to move up and down with the rest of the market or along with an index. This contrasts with a fixed interest rate, in which the interest rate of a debt obligation stays constant for the duration of the agreement.

A floating interest rate can also be referred to as a variable interest rate because it can vary over the duration of the debt obligation. 



|||For example, residential mortgages can be obtained with a fixed interest rate, which is static and can't change for the duration of the mortgage agreement, or with a floating interest rate, which changes periodically with the market. In the case of floating interest rates in mortgages, and most other floating rate agreements, the prime lending rate is used as a basis for the floating rate, with the agreement stating that the interest rate charged to the borrower is the prime interest rate plus a certain spread.