The employee utilization rate gives a measure of the billability of an employee's time (work hours). It is calculated as:
Utilization % = Billable Hours / Total Hours x 100
where Billable Hours are billable actual hours (of projects other than marketing and overhead) and Total Hours are determined based on what is selected in the Utilization Based On field in Settings > Company > Work Time. It can be based on total actual hours logged, standard working hours or standard working hours less deductions. Check out the description of this field in the Company article for more details.