How can I be sure the square footage is calculated correctly?

Only pay for the space you get by double checking landlord measurements of rental spaces. Commercial tenants often overpay for their spaces because of the inaccurate measuring of the premises. “Phantom space,” the extra space listed on lease agreements that does not actually exist, costs you extra money in base rent and CAM, and quickly adds up over a 10-year term. Before you sign, measure the space yourself and recalculate the rent based on the actual square footage delivered.