You are asking about the Money supply, this is a statistic kept by the US Federal reserve:
- M1 consists of (1) currency outside the U.S. Treasury, Federal Reserve Banks, and the vaults of depository institutions; (2)
traveler's checks of nonbank issuers; (3) demand deposits at
commercial banks (excluding those amounts held by depository
institutions, the U.S. government, and foreign banks and official
institutions) less cash items in the process of collection and Federal
Reserve float; and (4) other checkable deposits (OCDs), consisting of
negotiable order of withdrawal (NOW) and automatic transfer service
(ATS) accounts at depository institutions, credit union share draft
accounts, and demand deposits at thrift institutions. Seasonally
adjusted M1 is constructed by summing currency, traveler's checks,
demand deposits, and OCDs, each seasonally adjusted separately.
- M2 consists of M1 plus (1) savings deposits (including money market deposit accounts); (2) small-denomination time deposits (time
deposits in amounts of less than $100,000), less individual retirement
account (IRA) and Keogh balances at depository institutions; and (3)
balances in retail money market mutual funds, less IRA and Keogh
balances at money market mutual funds. Seasonally adjusted M2 is
constructed by summing savings deposits, small-denomination time
deposits, and retail money funds, each seasonally adjusted separately,
and adding this result to seasonally adjusted M1.
It appears they update the numbers every week.