Office space utilization is typically calculated by measuring the amount of floor space that's dedicated to office use, and then dividing that number by the total amount of floor space in the building. This gives you a percentage of how much office space is being used. There are a few other factors that can be included in the calculation, such as how much of the office space is being used for cubicles vs. private offices, or how many people are actually working in the office at any given time. But the basic calculation is simply measuring floor space and dividing by total floor space.