Converting start and end time columns to hours

[BlondeMoment]

This has probably been asked a million times before but I cannot find it easily in any help lookups.
I have one column of start time (09:00) and one column of end time(17:00). I want to convert these times to hours worked in a third column. Can anyone tell me the formula?If possible less the one break in a separate column? Many thanks.

 

[fairwinds]

Hi,

=(B2-A2+(B2 < A2)) and format as [h]:mm

or

=(B2-A2+(B2 < A2))*24 and format as general



(the +(B2 < A2) part is to cater for times passing midnight)