Hello Gavin,

If I understand you, the hours worked are entered in hours:minutes
format, eg. 7:00 is entered if 7 hours are worked on a particular day.

This formula should work for you:

=24*SUM(A10:A30)-144

(But instead of A10:A30, use whatever range has the daily hours
worked.)

YOU ALSO NEED TO FORMAT THE CELL to something other than a Date or Time
format. I recommend using the Number format, with 2 or 3 decimal
places.

The factor of 24 is needed because when you enter numbers in
hours:minutes format, Excel internally converts it to a fraction of a
day. For example, if somebody works 6 hours one day, and you enter
6:00, Excel will consider the number to be 0.25 (6 hours is 0.25 days),
EVEN THOUGH it is displaying it as "6:00".

Hope this helps,

Mark