The Federal Reserve uses two definitions of the money supply, M1 and M2. As panel (a) shows, more than half of M1 consists of checkable bank deposits with currency in circulation making up virtually all of the rest. M2, as panel (b) shows, has a much broader definition: it includes M1 plus a range of other deposits and deposit-like assets, making it over four times as large.
Source: Federal Reserve Bank of St. Louis.