Ask the leasing agent for the gross leasable area (GLA) of the building. This represents the total amount of square footage that can be rented out to tenants.
Find the amount of square feet of the space that you want to rent. Look on the marketing or real estate flyer, or ask the leasing agent for this information.
Divide the square footage of your desired space by the GLA. This will give you the percentage that will be your portion of the total common area maintenance fees. For example, if your space is 1,000 square feet and the GLA is 10,000 square feet, then your share of expenses is 10 percent (1,000/10,000=0.1 or 10 percent).