--- title: "Fractional Reserve Banking | Principles of Economics" description: "Fractional reserve banking is the system where banks keep part of deposits as reserves and lend the rest, creating money and shaping bank stability." canonical: "https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking" type: "key-term" subject: "Principles of Economics" unit: "Unit 27" --- # Fractional Reserve Banking | Principles of Economics ## Definition Fractional reserve banking is the banking system where banks keep only a fraction of deposits as reserves and lend out the rest. In Principles of Economics, it explains how banks create money and why bank runs can happen. ## What It Is Fractional reserve banking is the system Principles of Economics uses to explain how banks can create money instead of just storing it. A bank keeps some deposits in reserve so it can meet withdrawals, then lends the remaining funds to borrowers. That loan is the interesting part. When a bank makes a loan, it usually credits the borrower’s checking account rather than handing over stacks of cash. That new deposit becomes part of the money supply, which is why one original deposit can lead to a much larger total amount of spendable money in the economy. The size of that expansion depends on the reserve requirement and on how much banks actually choose to hold above the minimum. If the reserve requirement is 10%, a bank only needs to keep 10 cents of every dollar on reserve, at least in the simplest textbook version. The rest can be lent out, deposited again in another bank, and lent again, creating the money multiplier effect. This is also why fractional reserve banking is tied to liquidity. Deposits are available on demand for customers, but banks do not keep all of those deposits sitting idle. They rely on the idea that not everyone will withdraw at once, which is usually true. In normal conditions, the system keeps credit flowing and helps households and firms finance spending, investment, and day to day transactions. The risk shows up when confidence breaks down. If too many depositors try to withdraw money at the same time, the bank may not have enough cash on hand, even if it owns loans and other assets on paper. That is a bank run, and it can spread fear to other banks, reduce lending, and shrink the money supply. So fractional reserve banking is not just about lending. It is the mechanism that links deposits, reserves, bank credit, and financial stability in one system. ## Why It Matters Fractional reserve banking sits at the center of the banking unit in Principles of Economics because it connects three big ideas: how banks make profit, how money gets created, and why the financial system can become unstable. If you understand this system, a lot of later topics make more sense, especially reserve requirements, the money multiplier, and bank runs. It also gives you a better way to read real bank behavior. Banks do not simply hold deposits in a vault and wait. They manage reserves, issue loans, and balance safety against profitability. That tradeoff shows up in questions about why banks lend, why they care about liquidity, and why regulators watch them closely. The concept matters for central banking too. The Federal Reserve can influence the economy partly by changing rules and conditions that affect lending. Even when the reserve requirement is low, banks’ willingness to lend affects how much new money actually enters circulation. In class, this term often comes up when you are tracing the path of money through the banking system or explaining why a financial panic can spread beyond one bank. It turns a simple deposit into a chain reaction of credit creation, which is exactly why it is such a useful idea in macroeconomics. ## Connections ### Reserve Requirement This is the minimum fraction of deposits a bank must keep on hand. Fractional reserve banking only works because banks are allowed to lend out the rest, so the reserve requirement sets the floor for how much can be loaned under the textbook model. ### Money Multiplier The money multiplier describes how an initial deposit can expand into a larger amount of money through repeated lending and redepositing. Fractional reserve banking is the system that makes that expansion possible, while reserve rules and bank behavior affect how large the multiplier actually becomes. ### Bank Run A bank run happens when many depositors try to withdraw money at once. Fractional reserve banking creates the conditions for this risk because banks do not keep every deposited dollar available in cash. ### [Deposit Expansion](/principles-econ/key-terms/deposit-expansion) Deposit expansion is the process of new deposits being created as banks lend money and borrowers spend it. Fractional reserve banking is the mechanism behind that process, so this term is often used when showing the step by step growth of the money supply. ## On the AP Exam A quiz item or problem set usually asks you to trace what happens after an initial deposit, identify how reserves limit lending, or explain why the money supply can grow. You might also get a scenario about a bank losing deposits and need to connect fractional reserve banking to liquidity problems or a bank run. When you see a graph, table, or short case, look for the chain from deposits to loans to new deposits. If the question asks why banks do not lend every dollar, the answer is reserves and withdrawal risk. If it asks how banks create money, the answer is that loans create new deposits, not just a transfer of existing cash. For essay or discussion prompts, this term works well when you explain both sides of the system: it supports lending and economic activity, but it can also make the system vulnerable when confidence drops. ## Fractional Reserve Banking vs Reserve Requirement These are related but not the same. Fractional reserve banking is the overall system where banks keep only part of deposits as reserves and lend the rest, while the reserve requirement is the specific rule that sets how much must be held. Think of the requirement as the regulation and fractional reserve banking as the banking model. ## Key Takeaways - Fractional reserve banking is the system where banks keep only part of deposits in reserve and lend the rest. - When banks make loans, they create new deposits, which means they help expand the money supply. - The reserve requirement and bank behavior affect how much money can be created through repeated lending. - The system supports credit and spending, but it also creates liquidity risk if many depositors want cash at the same time. - A bank run is one of the clearest dangers tied to fractional reserve banking because banks cannot pay everyone instantly with cash on hand. ## FAQs ### What is fractional reserve banking in Principles of Economics? It is the banking system where banks keep only a fraction of deposits as reserves and lend out the rest. In Principles of Economics, it is the main idea used to explain how banks create money and how bank runs can happen. ### How does fractional reserve banking create money? When a bank makes a loan, it usually credits the borrower’s account with a new deposit instead of handing over existing cash. That deposit becomes part of the money supply, and when the borrower spends it, the funds can end up deposited in another bank and lent again. ### Is fractional reserve banking the same as a reserve requirement? No. Fractional reserve banking is the system, while the reserve requirement is the rule that tells banks how much of their deposits they must keep on reserve. The rule affects how much lending can happen, but it is not the whole system. ### Why can fractional reserve banking lead to bank runs? Banks do not keep all deposits as cash, so they cannot pay every depositor at once if everyone tries to withdraw together. If people lose confidence in the bank, that mismatch between liquid cash and outstanding deposits can trigger a run. ## Related Study Guides - [27.2 Measuring Money: Currency, M1, and M2](/principles-econ/unit-27/2-measuring-money-currency-m1-m2/study-guide/EQaqbtrZHHmUVhEV) - [28.1 The Federal Reserve Banking System and Central Banks](/principles-econ/unit-28/1-federal-reserve-banking-system-central-banks/study-guide/FLBtGqukSsg28lTz) - [27.3 The Role of Banks](/principles-econ/unit-27/3-role-banks/study-guide/Q0NjWQuHMuphuk4N) - [27.4 How Banks Create Money](/principles-econ/unit-27/4-banks-create-money/study-guide/RWE3NeRXWNKAK9ya) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking#resource","name":"Fractional Reserve Banking | Principles of Economics","url":"https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:24:05.230Z","isPartOf":{"@type":"Collection","name":"Principles of Economics Key Terms","url":"https://fiveable.me/principles-econ/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking#term","name":"Fractional Reserve Banking","description":"Fractional reserve banking is the banking system where banks keep only a fraction of deposits as reserves and lend out the rest. In Principles of Economics, it explains how banks create money and why bank runs can happen.","url":"https://fiveable.me/principles-econ/key-terms/fractional-reserve-banking","inDefinedTermSet":{"@type":"DefinedTermSet","name":"Principles of Economics Key Terms","url":"https://fiveable.me/principles-econ/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is fractional reserve banking in Principles of Economics?","acceptedAnswer":{"@type":"Answer","text":"It is the banking system where banks keep only a fraction of deposits as reserves and lend out the rest. In Principles of Economics, it is the main idea used to explain how banks create money and how bank runs can happen."}},{"@type":"Question","name":"How does fractional reserve banking create money?","acceptedAnswer":{"@type":"Answer","text":"When a bank makes a loan, it usually credits the borrower’s account with a new deposit instead of handing over existing cash. That deposit becomes part of the money supply, and when the borrower spends it, the funds can end up deposited in another bank and lent again."}},{"@type":"Question","name":"Is fractional reserve banking the same as a reserve requirement?","acceptedAnswer":{"@type":"Answer","text":"No. Fractional reserve banking is the system, while the reserve requirement is the rule that tells banks how much of their deposits they must keep on reserve. The rule affects how much lending can happen, but it is not the whole system."}},{"@type":"Question","name":"Why can fractional reserve banking lead to bank runs?","acceptedAnswer":{"@type":"Answer","text":"Banks do not keep all deposits as cash, so they cannot pay every depositor at once if everyone tries to withdraw together. If people lose confidence in the bank, that mismatch between liquid cash and outstanding deposits can trigger a run."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Principles of Economics","item":"https://fiveable.me/principles-econ"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/principles-econ/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 27","item":"https://fiveable.me/principles-econ/unit-27"},{"@type":"ListItem","position":4,"name":"Fractional Reserve Banking"}]}]} ```