Thanks for an interesting question, you gave me a good reason to
refresh my memory on this topic.
The Federal Reserve keeps track of money in circulation - there are
three such measures called M1, M2 and M3; they are beautifully
explained by the New York Federal Reserve Board here -
I believe that what you are looking for is M1, but you will be able to
determine this yourself once you review the three definitions.
The Fed reports on the level of these three indicators on a weekly
basis - you can view the latest data here -
For example, as of May 5th, seasonally-adjusted M1, based on a 13-week
average, was 1,235 billion dollars. You can also view a breakdown by
type for M1 - for example, the breakdown for the May 5th number is as
Currency - 643.4 billion dollars
Travelers checks - 7.3 billion dollars
Demand Deposits - 311.2 billion dollars
At community banks - 158.9 billion dollars
At thrift institutions - 131.8 billion dollars
Please let me know if this is the information you had been seeking. I
will be glad to clarify further or conduct additional research as
m1 "federal reserve" "currency in circulation"