Banks earn money from the difference between what they pay depositors and what they charge borrowers
A commercial bank takes in deposits from customers, pays those customers a small amount of interest, then lends that money out at a higher interest rate. The gap between what the bank pays you to hold your money and what it charges someone else to borrow that money is the bank's primary source of income. If a bank pays you 0.01% interest on a savings account but charges a borrower 6% on a mortgage, the bank keeps roughly 5.99% as profit on that transaction.
This model works because banks are middlemen. They aggregate small deposits from thousands of people into a pool large enough to make big loans to businesses and homebuyers. A single person cannot lend $300,000 to a developer, but a bank holding deposits from 10,000 customers can. The bank takes the risk that borrowers will repay, and it keeps the interest spread as compensation for that risk.
Key Takeaways
- The interest spread—the difference between deposit rates and loan rates—is how banks make most of their money.
- Banks also charge fees for services like overdrafts, wire transfers, account maintenance, and loan origination.
- Banks invest deposited money in bonds, stocks, and other securities, and keep the returns above what they pay depositors.
- When interest rates rise, banks can widen their spreads because they can charge borrowers more while still paying depositors low rates.
- Banks manage risk by setting aside capital reserves and by diversifying across many borrowers so one default does not wipe out profits.
How the interest spread works in practice
When you deposit $10,000 in a savings account earning 0.05% annually, the bank pays you $5 per year. That same bank then lends $10,000 to a small business at 8% interest, earning $800 per year. The bank's gross profit on that pair of transactions is $795 before operating costs.
The bank does not lend out every dollar it takes in. Banking regulations require banks to hold a portion of deposits as capital reserves—money they cannot lend out. The Federal Reserve sets a reserve requirement, which varies but is typically around 10% for large banks. So if a bank takes in $100 million in deposits, it can lend out roughly $90 million and must hold $10 million in reserve. This reserve protects depositors if loans go bad and borrowers cannot repay.
The spread also shifts with economic conditions. When the Federal Reserve raises interest rates, banks can charge borrowers more immediately, but they also have to pay depositors more to keep their money in the bank. Banks that move quickly to raise deposit rates less than they raise loan rates can widen their spread. When rates fall, the opposite happens—spreads often shrink because banks cannot lower loan rates as fast as they lower what they pay depositors.
Fees are the second major income stream
Beyond interest, banks charge fees for dozens of services. An overdraft fee ($30–$35 per incident) is one of the most visible. A wire transfer fee ($15–$30) is another. Monthly account maintenance fees, ATM fees charged to non-customers, loan origination fees (often 0.5% to 1% of the loan amount), and credit card annual fees all add up.
For a large bank, fee income can represent 30% to 40% of total revenue. A bank with $100 billion in deposits might collect $500 million annually in fees alone. Overdraft fees are particularly profitable because they apply to customers who are already short on money and cannot easily switch banks. Credit card late fees and foreign transaction fees work the same way—they target customers in a weak negotiating position.
Business customers pay fees for cash management services, merchant processing (the bank takes a cut when a business accepts card payments), and account analysis. These fees are often negotiated but are a steady source of income that does not depend on interest rates.
Investment income and securities trading
Banks do not sit on deposits as cash. They invest in bonds, mortgage-backed securities, stocks, and other financial instruments. A bank might buy a 10-year Treasury bond yielding 4%, hold it for a year, and sell it for a profit if rates fall. Or it might buy a pool of mortgages from another lender, collect the interest payments, and sell the pool later.
Large banks also have trading desks that buy and sell securities for profit. A trader might buy a stock at $50 and sell it at $52, keeping the $2 spread. Over thousands of trades per day, this adds up. Investment income is less stable than interest income because it depends on market conditions, but it can be substantial in good years.
Banks also earn fees by managing investment portfolios for wealthy customers and by underwriting securities offerings for corporations. When a company goes public, the bank that manages the initial public offering takes a percentage of the money raised. These investment banking services are a major profit center for large banks.
How banks manage the risk of lending
Not every borrower repays. A bank that lends $1 million to 100 small businesses knows that some will fail. The bank prices this risk into the interest rate—riskier borrowers pay higher rates. A borrower with poor credit might pay 12% while a borrower with excellent credit pays 4%. The difference compensates the bank for the higher probability of default.
Banks also diversify. Instead of lending all their money to one industry or one region, they spread loans across many borrowers, industries, and geographies. If the construction industry collapses, a bank that lent heavily to construction will suffer, but a bank with loans spread across construction, retail, healthcare, and manufacturing will weather the downturn better.
Regulators require banks to set aside capital based on the risk of their loan portfolio. A bank with mostly low-risk mortgages can lend out a higher percentage of its deposits than a bank with many high-risk business loans. This capital requirement acts as a buffer—if loans go bad, the bank's own capital absorbs the loss before depositors are harmed.
The role of the Federal Reserve and interest rates
The Federal Reserve does not set interest rates directly, but it sets the federal funds rate—the rate at which banks lend to each other overnight. This rate influences all other interest rates in the economy. When the Fed raises the federal funds rate, banks raise the rates they charge borrowers. When the Fed lowers it, banks lower their rates.
Banks benefit when the Fed raises rates because they can charge borrowers more while paying depositors less—at least initially. A bank that has locked in low rates on deposits can widen its spread significantly when the Fed tightens. Conversely, when the Fed cuts rates, banks suffer because they have to lower loan rates faster than they can lower deposit rates, and spreads compress.
This is why bank stocks often rise when the Fed signals it will raise rates and fall when the Fed signals it will cut rates. Investors understand that higher rates mean wider spreads and higher bank profits.
How size and scale affect bank profitability
Large banks have advantages that smaller banks do not. A bank with $500 billion in deposits can negotiate better rates on the bonds and securities it buys. It can spread its fixed costs—the salaries of executives, the cost of technology, the cost of branches—across a much larger revenue base. A bank with $5 billion in deposits has to pay similar regulatory costs but generates far less revenue.
Large banks also have access to cheaper funding. They can borrow in wholesale markets at rates close to the federal funds rate, then lend that money out at much higher rates. A small bank has to rely more heavily on deposits, which means it has to pay competitive rates to attract and keep customers.
Scale also allows large banks to invest in technology and risk management systems that smaller banks cannot afford. These systems reduce losses from fraud and bad loans, which improves profitability. The largest banks are also considered "too big to fail," which means the government will likely bail them out if they face a crisis. This implicit government backing lowers their borrowing costs further.
Frequently Asked Questions
Why do banks pay such low interest rates on savings accounts?
Banks pay low rates because they have abundant deposits. Millions of people keep money in savings accounts for safety, not returns. Because demand for deposit accounts is high and supply of deposits is abundant, banks can pay very little. If rates rose significantly, banks would have to pay more to depositors, which would shrink their profit margins.
Do banks make money when interest rates are low?
Banks make less money when rates are very low because the spread between what they pay depositors and what they charge borrowers shrinks. However, they still make money through fees, investment income, and by lending at rates above zero. During periods of very low rates, banks often increase fees to compensate for narrower spreads.
What happens to a bank if too many borrowers default?
If defaults exceed the bank's capital reserves, the bank can become insolvent. The Federal Deposit Insurance Corporation (FDIC) insures deposits up to $250,000 per account, so depositors are protected. The bank itself may fail, be taken over by regulators, or be acquired by another bank. Shareholders lose money, but depositors are made whole.
Can a bank run out of money?
A bank can face a liquidity crisis if too many depositors withdraw money at once, but this is rare because banks hold reserves and can borrow from the Federal Reserve. During the 2008 financial crisis, some banks did fail because they had invested heavily in bad mortgages and could not raise cash quickly enough. Modern regulations require banks to hold more liquid assets to prevent this.
How do online banks make money if they have no branches?
Online banks have lower operating costs because they do not maintain physical branches or employ as many tellers. They use the same interest spread model as traditional banks but can offer higher deposit rates and lower loan rates because their costs are lower. They also charge fewer fees, but they still profit from the spread and from investment income.