One way:

A1: <start time
B1: <end time
C1: =MOD(B1-A1,1) - (MOD(B1-A1,1)TIME(5,30,1))/48

Note, the 1 second in TIME(5,30,1) should prevent any rounding errors
from inadvertently taking off a lunch period at exactly 5.5 hours,
assuming you only enter time in hours and minutes.

In article ,
LGrobe wrote:

I am trying to figure time worked on a daily basis. I have done this
formula before, but have forgotten how to complete it.

My times look like (2nd shift hours)
3:30 PM
12:30 AM
The formula needs to calculate hours worked greater than 5.5 to take
out 1/2 hour lunch, and hours worked less than 5.5 to calculate total
hours with no lunch. We do not clock in and out for lunch breaks, it
is an automatic deduction, but somebody has earased my formula.

Please help!!