The load center is the horizontal distance from the vertical face of the forks to the load's center of gravity, the figure on which a forklift's rated capacity is based.
Rated capacity on the data plate is stated at a specific load center. OSHA’s eTool explains the physics: the front wheel axle is the fulcrum, and the load moment is the load weight multiplied by its distance from the fulcrum, so a 3,000 pound load at 24 inches creates a moment of 72,000 inch-pounds. Moving the same load further out increases the moment, which reduces the weight the truck can lift without tipping forward.
Long, deep or unevenly packed loads, attachments such as clamps or rotators, and loads not pushed back against the fork carriage all move the load center forward. The capacity at the actual load center comes from the data plate or the manufacturer, not from estimating by hand. Exceeding it is a common route to a forward tip-over or a dropped load. See forklift load center.