Office space for lease is priced per square foot per year, so you need to know the exact square foot of your space. The typical office is 10 feet by 12 feet so, if you are leasing three offices, that is 120 square feet per office totaling 360 square feet; however, also factored in is the common area, which is the lobby, hallways, bathrooms, utility rooms such as janitorial closets and mechanical rooms, but not vertical space such as stairwells and elevators. This ratio of rentable square feet to usable square feet is called the core factor and is multiplied by your square footage leased. For more information on office leasing, read our article Office Market Trends.