What is the weight per square foot capacity of a typical commercial bookcase shelf?

A commercial bookcase shelf rated at 75 lbs. over a 36 in. width and 12 in. depth provides approximately 25 lbs. per square foot of capacity, which is sufficient for dense book and binder storage (books weigh approximately 15–25 lbs. per linear foot). Heavy-duty units rated at 150 lbs. per shelf provide approximately 50 lbs. per square foot. OfficeFurniture2go.com provides load ratings for all products — call 1-800-460-0858.