Overloading a forklift can result in an extremely dangerous situation. There are some 100,000 forklift related injuries and 100 deaths each year in the United States. Overloaded lifts are a contributing factor in many of these. Sadly most of these accidents and injuries could be avoided if operators would properly calculate the load capacity of their machines.
Locate the data plate on the forklift. Normally these are located on the hood of the machine just beside the operator's seat. The plate will be rectangular and covered with numbers and a chart showing weight limits at various heights. All of the data needed to calculate the forklifts load capacity is located on this data plate. The data plate cannot be removed or altered for any reason expect by the manufacturer or other authorised person(s).
Determine the load centre of the item or material you are attempting to lift. If your forklift has a rated load capacity of 1.81 Kilogram, this capacity is based on a load centre of 24 inches from the backrest and 24 inches above the forks. This capacity will change as the load is raised, or the forks are titled forward. If your load centre is 48 inches from the backrest and 24 inches from the forks, your load capacity will be greatly reduced. The further the load centre is from the back rest the lower your lifting capacity will be. This capacity is reduced further as the load is raised. The chart on the data plate will show the machines capacity at various load centres and at various heights. You should never exceed these limits.
Understand the stability triangle of the forklift. To form this triangle draw a line between the front wheels, then from the each end of this line draw another line to the centre of the back axle. This is the stability triangle. When the forklift is empty the COG (centre of gravity) will be located in the triangle near the rear axle. As the load is lifted the COG moves forward. As the forklift turns left or right, the COG shifts away from the direction of the turn. Should the COG ever go outside of the triangle the machine will overturn. The heavier the load being lifted the faster the COG will shift toward the front axle and the more rapidly it will shift from side to side in turns.
You should study the data plate of your machine prior to beginning work. While you will still need to consult the chart, you will have a good base knowledge and understanding of the limits of your machine.
Be aware load capacities are listed for ideal conditions. If operating a machine on uneven or rough terrain or other unusual conditions the load capacity can change dramatically.