In banking, what are a bank's "reserves"?
Choose an answer, then check it.
Economics · Foundations
Banking
On this page 9 sections
In 30 seconds
Banks are financial intermediaries: they pool money from savers and lend it to borrowers. Because depositors rarely all withdraw at once, a bank keeps only a fraction of deposits as Reserves The portion of deposits a bank keeps as cash on hand or at the central bank rather than lending or investing it. Full entry → and lends out the rest. Each new loan becomes a new deposit somewhere else, so the banking system as a whole creates money. That same fractional-reserve design is why bank runs can happen and why Deposit insurance A government guarantee that repays depositors up to a set limit if their bank fails, removing the incentive to run. Full entry → exists to stop them.
Why this matters
Most of the money in a modern economy is not printed by a government; it is created by ordinary banks making loans. Understanding Fractional-reserve banking A system in which banks hold only a fraction of deposits as reserves and lend out the remainder. Full entry → explains where money actually comes from, why credit expands in booms and contracts in busts, and why a rumor can topple a solvent bank in hours. It also clarifies the safeguards you rely on without thinking: deposit insurance that protects your checking account, and the capital and reserves that keep the payment system standing. For anyone studying economics, finance, or public policy, banking is the machinery linking savers, borrowers, and the money supply.
The college version
Banks as financial intermediaries
A bank sits between two groups who rarely meet directly: savers who have money they do not need right now, and borrowers who want money they do not yet have. By accepting deposits from the first group and making loans to the second, a bank acts as a Financial intermediary An institution that stands between savers and borrowers, taking in deposits and using them to make loans. Full entry →. This arrangement lowers the cost and risk of connecting the two sides. A saver would struggle to find a trustworthy borrower, judge their creditworthiness, and enforce repayment; a borrower would struggle to assemble a large loan from many small savers. The bank pools thousands of deposits, spreads its lending across many borrowers, specializes in screening and monitoring, and profits from the gap between the interest it pays depositors and the higher interest it charges borrowers. Depositors gain safety, liquidity, and a small return; borrowers gain access to credit; the economy gains a mechanism for channeling idle savings into productive investment.
Reading a bank's balance sheet
A bank's balance sheet lists what it owns (assets) against what it owes (liabilities), with the difference belonging to the owners. The main assets are reserves (cash held in the vault or on deposit at the central bank), loans the bank has made, and bonds or other securities it holds. The main liability is deposits: the checking and savings balances customers can withdraw, which the bank owes back to them. This is the point that trips people up. Your deposit is your asset, but on the bank's books it is a liability, because the bank owes you that money. The difference between total assets and total liabilities is the bank's net worth, also called bank capital. A healthy bank has positive net worth: its assets exceed what it owes. If enough loans go bad, asset values fall, and net worth can shrink toward or below zero, which is the definition of insolvency. Capital is therefore a cushion that absorbs losses before depositors are threatened.
Fractional-reserve banking and money creation
Because depositors do not all demand their money on the same day, a bank does not need to keep every deposited dollar in the vault. It keeps only a fraction as reserves and lends or invests the rest. This is fractional-reserve banking, and it is the engine of money creation. Suppose you deposit $1,000 and the bank keeps 10 percent, lending $900 to someone else. That borrower spends the $900, and whoever receives it deposits it in their own bank, which keeps $90 and lends $810, and so on. At each step a new loan becomes a new deposit, and deposits are money. No bank prints currency; the banking system as a whole expands the money supply simply by lending. This is why most of the money in a modern economy is not physical cash but deposit balances created through lending. Money is destroyed in reverse: when loans are repaid faster than new ones are made, deposits shrink and the money supply contracts.
The money multiplier
The Money multiplier An estimate of how much total money the banking system can create from new reserves, equal in the simple case to one divided by the reserve ratio. Full entry → estimates how much total money a fresh injection of reserves can support. In its simplest form it equals one divided by the Reserve ratio The fraction of its deposits that a bank holds as reserves rather than lending out. Full entry →, the fraction of deposits banks hold as reserves. Work a standard example. A bank receives $10 million in deposits and faces a 10 percent reserve ratio, so it holds $1 million and lends $9 million. With a reserve ratio of 0.10 the simple multiplier is 1 / 0.10 = 10. Tracing the $9 million as it is spent, redeposited, and re-lent across many banks, the system creates about 10 x $9 million = $90 million in new money, and total deposits across the system rise to roughly $100 million. The simple multiplier is a ceiling, not a forecast. Two leakages make the real figure smaller. First, people hold some cash outside banks rather than redepositing it, which stops the chain. Second, banks often keep excess reserves above any required minimum, especially when they are cautious, so less is lent at each round. The size of the reserve ratio itself is shaped by rules the central bank sets and by banks' own choices, which the Federal Reserve topic takes up.
Bank runs and deposit insurance
The same design that lets banks create money also makes them fragile. Because a bank lends out most of what it takes in and keeps only limited reserves, it cannot pay every depositor at once. A Bank run A rush by many depositors to withdraw at once, usually triggered by fear that the bank is or will become insolvent. Full entry → occurs when depositors, fearing the bank has or will have negative net worth, rush to withdraw before the cash runs out. The fear can be self-fulfilling: even a false rumor, if enough people act on it, can drain a solvent bank and force it to close. During the Great Depression, waves of bank runs shut thousands of banks. The main U.S. safeguard is deposit insurance. The Federal Deposit Insurance Corporation, created in 1933, guarantees deposits so that customers are repaid even if their bank fails, which removes the reason to run. The standard coverage is $250,000 per depositor, per insured bank, per ownership category; that figure was made permanent by the Dodd-Frank Act, effective July 22, 2010. A second safeguard, the central bank acting as lender of last resort, is covered in the Federal Reserve topic. This lesson keeps to why runs happen and how insurance defuses them; it does not offer personal financial advice.
Eli explains
The same idea, in plain words
Explain it like I’m 10
A bank is a middleman for money. People who have spare money park it at the bank, and the bank lends most of it to people who need money now, keeping only a little in the drawer for anyone who comes to withdraw. Here is the surprising part: when the bank makes a loan, it does not hand over a pile of cash from the vault. It just adds numbers to the borrower's account. That new balance is real money the borrower can spend, so lending actually makes new money appear. It only works because not everyone asks for their money back on the same day.
Picture it like this
Think of a coat check at a huge concert. Hardly anyone leaves early, so the attendant quietly lends out most of the coats to a nearby theater for the evening, keeping a few by the door for the rare person who leaves at intermission. Everything is fine, until a rumor spreads that the coats are gone and the whole crowd storms the counter at once.
Where the picture stops working
The analogy breaks down in an important way. A coat check only moves existing coats around, but a bank does something a coat check cannot: by lending, it creates brand-new money that did not exist before, rather than just relocating what was handed in. And a real bank is protected by deposit insurance, so the panic that would doom the coat check usually never starts.
Worked example
Start with $10 million deposited at a bank facing a 10 percent reserve ratio. The bank keeps $1 million (10 percent) in reserves and lends the other $9 million. That borrower spends the money, and the recipient deposits it at another bank, which keeps 10 percent and lends 90 percent, and so on down the chain. The simple money multiplier is 1 divided by the reserve ratio: 1 / 0.10 = 10. Applied to the $9 million first loan, the system can create about 10 x $9 million = $90 million in new money, lifting total deposits to roughly $100 million. In practice it is less, because some people hold cash outside banks and banks keep excess reserves, both of which break the chain early.
Key takeaway
Banks turn a fraction of held reserves into a much larger pool of money by lending, which is why the banking system creates most money, why runs are a built-in risk, and why deposit insurance exists.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
On a commercial bank's balance sheet, customer checking and savings deposits are recorded as which of the following?
Choose an answer, then check it.
A bank receives $20 million in new deposits and the reserve ratio is 25 percent. Using the simple money multiplier, what is the maximum new money the banking system can create from the amount this bank lends out?
Choose an answer, then check it.
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Explain how banks act as financial intermediaries between savers and borrowers.
- Identify the assets, liabilities, and net worth on a bank's balance sheet.
- Describe how fractional-reserve lending creates money across the banking system.
- Apply the simple money multiplier (1/reserve ratio) to a worked example and explain why the real-world figure is smaller.
- Analyze why bank runs occur and how deposit insurance defends against them.
Common mistakes
Thinking a deposit is an asset on the bank's books.
A deposit is your asset but the bank's liability, because the bank owes that money back to you.
Believing banks lend out physical cash they have stacked in the vault, one loan per pile.
Lending mostly credits a new deposit balance; the act of lending itself creates new money, and only a fraction is kept as cash reserves.
Treating the simple money multiplier (1/reserve ratio) as the exact amount of money created.
It is a maximum. Cash held outside banks and excess reserves banks choose to keep make the real multiplier smaller.
Assuming only a failing, badly run bank can suffer a run.
Because reserves are fractional, even a solvent bank can be forced to close if enough depositors withdraw at once on a false rumor.
Confusing FDIC deposit insurance with a guarantee on every kind of account for any amount.
Standard coverage is $250,000 per depositor, per insured bank, per ownership category, and applies to deposit accounts, not investments like stocks.
Easily confused
Reserves vs. Deposits
Reserves are an asset the bank holds (cash kept back); deposits are a liability the bank owes to customers.
Simple money multiplier vs. Actual money created
The simple multiplier (1/reserve ratio) is a maximum; real money creation is smaller because of cash leakages and excess reserves.
Illiquidity in a bank run vs. Insolvency
A run is a cash-timing problem that can hit a solvent bank; insolvency means liabilities actually exceed assets (negative net worth).
Key vocabulary
- Financial intermediary
- An institution that stands between savers and borrowers, taking in deposits and using them to make loans.
- Reserves
- The portion of deposits a bank keeps as cash on hand or at the central bank rather than lending or investing it.
- Fractional-reserve banking
- A system in which banks hold only a fraction of deposits as reserves and lend out the remainder.
- Net worth (bank capital)
- A bank's total assets minus its total liabilities; a positive value means the bank is solvent.
- Reserve ratio
- The fraction of its deposits that a bank holds as reserves rather than lending out.
- Money multiplier
- An estimate of how much total money the banking system can create from new reserves, equal in the simple case to one divided by the reserve ratio.
- Bank run
- A rush by many depositors to withdraw at once, usually triggered by fear that the bank is or will become insolvent.
- Deposit insurance
- A government guarantee that repays depositors up to a set limit if their bank fails, removing the incentive to run.
Sources & references
- Principles of Macroeconomics 3e, 14.3 The Role of Banks — OpenStax, Rice University
- Principles of Macroeconomics 3e, 14.4 How Banks Create Money — OpenStax, Rice University
- Principles of Macroeconomics 3e, 15.2 Bank Regulation — OpenStax, Rice University
- Deposit Insurance — Federal Deposit Insurance Corporation (FDIC)
- Deposit Insurance Regulations; Permanent Increase in Standard Coverage Amount — Federal Register (FDIC final rule)
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-19
Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.