---
title: "Fractional Reserve Banking | Principles of Macroeconomics"
description: "Fractional reserve banking is a system where banks keep part of deposits as reserves and lend the rest, expanding money supply in Principles of Macroeconomics."
canonical: "https://fiveable.me/principles-macroeconomics/key-terms/fractional-reserve-banking"
type: "key-term"
subject: "Principles of Macroeconomics"
unit: "Unit 14"
---

# Fractional Reserve Banking | Principles of Macroeconomics

## Definition

Fractional reserve banking is the system where banks keep only a fraction of deposits on hand as reserves and lend out the rest. In Principles of Macroeconomics, it explains how banks create money and why bank runs can happen.

## What It Is

Fractional reserve banking is the banking system used in Principles of Macroeconomics where banks hold only part of their depositors' money as reserves and loan out the rest. That means your deposit does not sit untouched in a vault, because most of it is available for lending, payments, and other bank activity.

Here is the basic flow: you deposit money in a checking or savings account, the bank keeps a required amount in reserve, and the remaining funds can be loaned to a borrower. When that loan is spent, the money often ends up back in another bank as a deposit, which lets the process repeat. That is why macroeconomics treats banks as money creators, not just money storage centers.

The reserve requirement is the rule that sets the minimum amount of deposits banks must keep available. A lower reserve requirement usually gives banks more room to lend, while a higher one leaves less room for lending. In class, this connects directly to the money multiplier, which describes how an initial deposit can lead to a larger total increase in deposits and loans across the banking system.

A simple example makes this clearer. If a bank must keep 10 percent of deposits in reserve, then a $1,000 deposit leaves $900 available to lend. That $900 is spent and redeposited somewhere else, where another bank can lend out most of it again. The original deposit does not disappear, but it can support multiple rounds of lending and deposit creation.

This system also creates risk. If many depositors try to withdraw at the same time, the bank may not have enough cash on hand, even if it is financially healthy on paper. That is the basic logic of a bank run, which is why regulation, deposit insurance, and central bank support matter in the banking system.

## Why It Matters

Fractional reserve banking sits right at the intersection of money, banks, and monetary policy in Principles of Macroeconomics. It explains why banks are more than safe deposit boxes, and why lending decisions can affect the total money supply in the economy.

You also need it to make sense of the Federal Reserve's tools. When the Fed changes reserve rules or influences interest rates, it is working through banks that use deposits to make loans. If banks lend more, money supply can expand more quickly. If banks are cautious or worried, that transmission slows down, even when the Fed is trying to stimulate the economy.

It also gives you the logic behind bank instability. A bank run is not just a panic scene in a movie, it is a direct result of fractional reserve banking because banks keep only part of deposits as reserves. That is why bank regulation, deposit insurance, and bank resolution exist in the banking system.

## Connections

### Reserve Requirement

The reserve requirement sets the legal minimum a bank must hold rather than lend out. Fractional reserve banking is the larger system, while the reserve requirement is one of the main rules that shapes how much lending that system allows. If the requirement changes, the amount of money banks can create through lending changes too.

### Money Multiplier

The money multiplier describes how an initial deposit can ripple through the banking system and create a larger total increase in deposits and loans. Fractional reserve banking is the mechanism that makes that possible, since each bank keeps a fraction and relends the rest. The multiplier helps you estimate the size of that expansion.

### [Bank Run](/principles-macroeconomics/key-terms/bank-run)

A bank run happens when many depositors try to withdraw their money at once because they fear the bank will not have enough cash. Fractional reserve banking creates the conditions for this because banks do not keep all deposits as reserves. A healthy bank can still fail if too many people panic at the same time.

### [Commercial Banks](/principles-macroeconomics/key-terms/commercial-banks)

Commercial banks are the institutions that actually do the lending, deposit taking, and reserve holding in this system. Fractional reserve banking describes how those banks operate in practice, not just what they are called. When you analyze a bank's balance sheet, you are seeing the fractional reserve model in action.

## On the AP Exam

A quiz question might ask you to trace what happens after a deposit enters the banking system. Your job is to show the reserve held back, the loan created from the remainder, and how that loan can become another deposit. On a problem set, you may also calculate the maximum expansion of deposits using the reserve requirement or money multiplier.

If you get a short-answer prompt about a bank run, connect the panic to the fact that banks do not keep all deposits in cash. If a graph or policy question mentions the Fed changing reserve rules, explain how that change affects bank lending and the money supply. The best answers do more than define the term, they show the chain from deposits to loans to money creation to possible instability.

## Fractional Reserve Banking vs Reserve Requirement

Reserve requirement is the rule or percentage that banks must keep on reserve, while fractional reserve banking is the entire system built around keeping only part of deposits available and lending the rest. One is the policy constraint, the other is the banking model it helps shape.

## Key Takeaways

- Fractional reserve banking is the system where banks keep only a fraction of deposits as reserves and lend the rest.
- This lending process can create new deposits and expand the money supply, which is why banks are part of money creation in macroeconomics.
- The reserve requirement limits how much banks can lend and helps shape the size of the money multiplier.
- The same system can make banks vulnerable to bank runs if depositors all want cash at the same time.
- Bank regulation and central bank oversight exist partly to keep this system stable enough to support the economy.

## FAQs

### What is fractional reserve banking in Principles of Macroeconomics?

It is the banking system where banks keep only part of deposits as reserves and loan out the rest. Those loans often become new deposits, so the banking system can expand the money supply. That is why it matters in macroeconomics, not just banking.

### How does fractional reserve banking create money?

When a bank makes a loan, it does not just move existing money around, it creates a new deposit for the borrower. If that money is spent and redeposited, the process can repeat across multiple banks. The result is a larger total amount of deposits in the economy.

### How is fractional reserve banking different from reserve requirement?

Fractional reserve banking is the whole system of holding only part of deposits as reserves and lending the rest. Reserve requirement is the specific rule that tells banks the minimum amount they must keep. So the requirement shapes the system, but it is not the system itself.

### Why can fractional reserve banking lead to bank runs?

Because banks do not keep all deposits in cash, they may not be able to satisfy every withdrawal request at once. If too many people panic and withdraw together, the bank can run short of liquid cash even if it made sound loans. That is why confidence and regulation matter.

## Related Study Guides

- [14.2 Measuring Money: Currency, M1, and M2](/principles-macroeconomics/unit-14/2-measuring-money-currency-m1-m2/study-guide/8nwGW8NUmeMdcY6q)
- [14.3 The Role of Banks](/principles-macroeconomics/unit-14/3-role-banks/study-guide/Cy0C2yNRIkZ3xPh2)
- [14.1 Defining Money by Its Functions](/principles-macroeconomics/unit-14/1-defining-money-functions/study-guide/OekBG4eo43Xacok9)
- [15.2 Bank Regulation](/principles-macroeconomics/unit-15/2-bank-regulation/study-guide/me8VPYOwpThZgOnh)
- [15.1 The Federal Reserve Banking System and Central Banks](/principles-macroeconomics/unit-15/1-federal-reserve-banking-system-central-banks/study-guide/s4SMlHD9Jaywktpv)

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