Money supply is the total supply of money circulating in a region or country. What is meant by money in circulation includes the money we use as a means of daily transactions such as coins and banknotes, balances in savings and checking accounts, and other types of money. Monye supply is also key to studying macroeconomics. The way to calculate the money supply is to add up all the types of money in circulation, or it will be easier if you look at the money supply data at your country's central bank.