What Is the Prime Interest Rate?

2 Ways Hikes in the Prime Rate Cost You Money

prime rate recipient
Only a bank's best customers receive the prime rate. Photo: Ariel Skelley/Getty Images

Definition: The prime interest rate is what U.S. banks charge their best customers. It's usually the best loan rate available to non-banks. It's also called the prime lending rate, the prime rate, or even just prime.

Banks base the prime rate on the federal funds rate.  That's the rate banks charge each other for special overnight loans. They borrow fed funds from each other to fulfill the Federal reserve requirement each night.

For example, on June 14, 2017, the Federal Open Market Committee raised this rate to 1.25 percent. A few hours later, U.S. Bancorp raised the prime rate to 4.25 percent. Find out the Current Federal Reserve Interest Rate.

Two Ways the Prime Rate Affects You

Banks base most interest rates on prime. That includes adjustable-rate loansinterest-only mortgages, and credit card rates. That means your monthly payment increases along with prime. Therefore, pay attention if you hear the Fed is raising the fed funds rate. It means your costs are about to increase.

Banks base these on rates on the prime rate, but the rate is a littler higher. That's because banks have a greater default risk. They've got to cover their losses for the loans that never get repaid. The riskiest loans are credit cards. That's why those rates are so much higher than prime. 

The prime rate affects liquidity in the financial markets.

A low rate increases liquidity by making loans less expensive and, therefore, easier to get. When prime lending rates are low, businesses expand and so does the economy. Similarly, when rates are high, liquidity dries up, and the economy slows down.

Prime Rate Versus Libor

Not all banks base their other interest rate on the prime rate.

International banks and large banks with a lot of foreign customers use Libor.  That's the London InterBank Offer Rate. It's the rate banks charge each other for short-term loans. 

The fed funds rate, Libor, and the prime rate normally move in tandem. The prime rate is usually about 1.5 points above Libor. That's typically a few tenths of a point above the fed funds rate.

When the rates don't move together, that indicates that something is very wrong with the financial markets. For example, in September 2007, the Fed lowered its funds rate down half a point. Libor didn't budge. Banks were afraid of getting subprime mortgage debt as collateral from each other. They kept Libor high to offset this risk. Banks were so afraid to lend to each other that they kept raising Libor even as the prime rate fell.

When the Fed lowered its interest rate from 5.25 percent to 4.75 percent on September 18, 2007, the prime rate also dropped, from 8.25 percent to 7.75 percent. Libor rose from 5.5 percent to 5.6 percent. As the Fed continued to lower its rate, the prime also fell. Libor bounced up and down. That indicated the high level of irrational fear between banks. (Source: "Historical Prime Rate," JPMorgan Chase.)

On October 8, 2008, when the Fed lowered its rate to 1.5 percent, the prime rate dropped to 4.5 percent. Unbelievably, it was barely above Libor, which stubbornly remained at 4.3 percent. That occurred weeks after the panicked run on money market funds that nearly brought the U.S. economy to collapse. This Fed rate cut was part of a coordinated effort among all the world's central banks to shore up the collapsing financial markets. It was only a few days after Congress passed the $700 bank bailout bill. Banks were in a state of sheer panic. For more, see 2008 Financial Crisis Timetable.

Soon afterwards, Libor slowly started returning to normal. When the Fed lowered its rate to zero in December 2008, the prime rate obediently fell to 3.25 percent. Libor dropped to 2.19 percent. It took another year before it returned to its typical range, a few tenths of a point above the Fed's rate.

​For more, see Libor Rate History