How many hours per week does the average U.S. worker work per week?

Hello roblevin-ga,

Thank-you for your question.

The U.S. Department of Labor/Bureau of Labor Statistics (BLS) can
provide you with this data.  It appears that they take measures of the
data every 3 months and the data is broken up into PRIVATE and
MANUFACTURING industry data.

Total Private Average Working Hours Per Week
YEAR     MARCH    JUNE     SEPT     DECEMBER
1995     34.4     34.3     34.3     34.3   
1996     34.1     34.3     34.3     34.4   
1997     34.4     34.5     34.6     34.6   
1998     34.6     34.5     34.5     34.5   
1999     34.4     34.4     34.4     34.4   
2000     34.4     34.3     34.2     34.2   
2001     34.1     34.0     33.9     33.8   
2002     33.8     33.9     33.9     33.8   
2003     33.8     33.6     33.6     33.7   
2004     33.7     33.7     33.7     33.7   
2005     33.7     33.7     33.8     33.8*

Manufacturing Average Working Hours Per Week
1995     41.7     41.2     41.2     41.1   
1996     40.7     41.3     41.5     41.5   
1997     41.6     41.7     41.6     41.9   
1998     41.7     41.4     41.4     41.5   
1999     41.3     41.3     41.5     41.4   
2000     41.5     41.4     41.2     40.9   
2001     40.5     40.4     40.4     40.1   
2002     40.3     40.6     40.5     40.4   
2003     40.3     40.2     40.3     40.7   
2004     40.9     40.9     40.8     40.5   
2005     40.6     40.4     40.6     40.9*  
* preliminary data

I have only duplicated the data for the last 10 years here but on the
BLS website the data goes back to 1939.

The data duplicated here was obtained from the following website:
http://data.bls.gov/PDQ/outside.jsp?survey=ce

Further information can be obtained here (including the link to the help pages):
http://www.bls.gov/ces/cesprog.htm

The information is in line with the many estimates that can be
gathered by a simple Google websearch (unfortunately most of these do
not back up their information with sources as I have done here).

So to answer your question, the average US worker works approximately
40-41 hours per week.

If you require any further assistance on this subject please do not
hesitate to ask for clarification and I will do my best to respond
swiftly.

Search Strategy:
http://www.bls.gov/aspsrch/query.idq?TextRestriction=%22average+weekly+hours%22&CiMaxRecordsPerPage=20&CiScope=%2F&TemplateName=query&CiSort=rank%5Bd%5D&HTMLQueryForm=%2Fsearch%2Fsearch%2Easp
://www.google.co.uk/search?q=%22average+american+works+a+*+hour+week%22

Terrific.