Variable Interest Rate

What Is a Variable Interest Rate?

A variable interest rate is an interest rate that can change during the life of a loan, bond, or other debt. Unlike a fixed interest rate, which stays the same from start to finish, a variable rate moves up or down in line with a reference rate. The cost of borrowing or the return on lending can therefore rise or fall over time. Variable rates are also called floating rates.

How It Works

Most variable rates are built from two parts. The first is a benchmark rate, a published reference rate that moves with market conditions. One example is the Secured Overnight Financing Rate (SOFR), which is used in U.S. dollar markets. The second is a fixed add-on called the margin, which the lender sets when the loan is made and which does not change. The basic relationship is:

Variable rate = benchmark rate + margin

The contract usually specifies how often the rate resets, such as monthly, quarterly, or annually. Many agreements also include an interest rate cap or floor that limits how far the rate can move.

An Example

Suppose a loan carries a margin of 2 percentage points above a benchmark. If the benchmark is 3%, the loan rate is 5%. If the benchmark rises to 4% at the next reset, the loan rate becomes 6%, and the borrower's interest payments increase. If the benchmark falls, the payments decrease. These figures are hypothetical and only illustrate the mechanism.

Advantages and Disadvantages

For borrowers, variable rates often start at a lower level than comparable fixed rates, though not always. They can also fall when market rates decline. The main drawback is uncertainty, because payments can rise and make budgeting harder.

For lenders and investors, variable rates reduce exposure to interest rate risk, since income adjusts as market rates move. The trade-off is that income can fall when rates drop.

Variable rates are common in adjustable-rate mortgage products, some credit cards, and floating-rate note bonds. Anyone reviewing a variable-rate loan or bond should check the reset schedule, the benchmark used, the margin, and any caps or floors in the terms.