Fundamentals

Money Supply: What It Is, How It Is Measured, and How It Differs from the Monetary Base

By Daniel Sardá · Published on June 12, 2026

4 min read800 words

The money supply groups different forms of money by liquidity. Understanding its aggregates helps analyze credit, prices, and monetary conditions.

The money supply is the set of forms of money available in an economy, measured according to how liquid they are. It includes cash, but also bank deposits and, in broader measures, certain instruments that can be turned into means of payment relatively easily.

There is no single number that captures everything that can be treated as money. That is why statistical authorities use several monetary aggregates: each one draws a different boundary between assets that can be used immediately and those that are somewhat less liquid.

Key idea: the money supply is not just bills and coins; it also includes money held in banks and, depending on the aggregate, other liquid assets.

Money supply, monetary base, and monetary aggregate

Although they often appear together, these expressions do not mean exactly the same thing.

The monetary base is the money created by the central bank. It consists mainly of cash and the reserves that commercial banks hold at that institution. The broad money supply, by contrast, also includes public deposits and other liquid instruments. Confusing the two measures is like treating bank reserves and a checking-account balance as if they were the same thing.

The phrase money supply is often used in general discussion as a synonym for monetary aggregate. In technical analysis, however, it is better to specify which aggregate is being observed, because speaking about “the amount of money” without defining its components can hide important differences.

How it is measured: from M1 to M3

Aggregates order money from the most liquid forms to progressively broader measures. Their exact components can vary by jurisdiction. In the euro area, for example, the European Central Bank uses this logic:

• M1 includes cash in circulation and demand deposits, which can be used immediately for payment.
• M2 includes M1 and adds certain short-term deposits or deposits with notice.
• M3 includes M2 and incorporates other liquid instruments, such as certain money market fund shares, repurchase agreements, and short-term debt securities.

Each broader aggregate includes the previous one. The point is not to decide which asset is the “real” money, but to provide different lenses for analyzing how much liquid purchasing power is available and how quickly it can be mobilized.

Key idea: M1 is the better measure of money that can be spent immediately; M2 and M3 widen the lens to assets close to money.

Who influences the amount of money

The central bank influences monetary conditions through its interest rates, operations, and supply of reserves. But it does not directly control every unit included in broad aggregates. The amount of money also depends on commercial banks, credit demand, and the decisions of households and firms.

When a bank grants a loan, it normally credits a deposit in the borrower’s account. That process can increase broad money. When the loan is repaid, the deposit that was created is reduced. The Bank of England stresses that this mechanism does not allow unlimited lending: risk, capital, regulation, demand, and monetary policy all matter.

So “printing money” describes only part of the phenomenon. In modern economies, a large share of the money used for payments exists as bank deposits, not as physical cash.

How it relates to inflation, credit, and activity

Looking at the money supply helps assess credit conditions, potential spending, and price trends. Sustained expansion can make more loans and spending possible; contraction can accompany tighter financial conditions.

However, a change in money supply alone does not make it possible to predict automatically how much prices will change or when. Transmission depends on how much money the public wants to hold, how much credit is demanded, how output evolves, and what expectations exist, among other factors. That is why monetary growth matters for studying inflation, but does not by itself explain short-run price changes completely.

Key idea: more money supply does not mean an immediate, proportional increase in all prices; what matters is how, when, and for what purpose that money circulates.

Common confusions

The money supply is not just cash, because it includes deposits and other liquid assets. It is also not identical to the monetary base, which is limited to central bank money. And an increase in the money supply does not by itself prove that banks are lending without constraint or that future inflation can be calculated with a simple rule.

Measuring it matters because it helps track how money and credit change within an economy. That information helps evaluate monetary stability, purchasing power, and the conditions under which people and firms make decisions. The useful reading always begins with a concrete question: what aggregate is being measured, and which forms of money does it include?