This formula calculates total working hours between two dates and times, that occur between a "lower" and "upper" time. In the example shown, the lower time is 9:00 AM and the upper time is 5:00 PM. These appear in the formula as the named ranges "lower" and "upper".
The logic of the formula is to calculate all possible working hours between the start and end dates, inclusive, then back out any hours on the start date that occur between the start time and lower time, and any hours on the end date that occur between the end time and the upper time.
The NETWORKDAYS function handles the exclusion of weekends and holidays (when provided as a range of dates). You can switch to NETWORKDAYS.INTL if your schedule has non-standard working days.
The result is a number which represents total hours. Like all Excel times, you will need to format the output with a suitable number format. In the example shown, we are using:
The square brackets stop Excel from rolling over when hours are greater than 24. In other words, they make it possible to display hours greater than 24. If you need a decimal value for hours, you can multiply the result by 24 and format as a regular number.
If start and end times will always occur between lower and upper times, you can use a simpler version of this formula:
No start time and end time
To calculate total work hours between two dates, assuming all days are full workdays, you can use an even simpler formula:
See explanation here for details.