One-ton trucks are the largest class of pickup truck in general production and are used mainly for hauling or towing heavy loads. Though the term "one-ton" initially referred to the maximum payload of trucks in this class, modern heavy-duty pickups can have payload capacities in excess of 6,000 pounds and towing capacities of up to 30,000 pounds when properly equipped.
The half-ton, three-quarter ton and one-ton pickup truck classification system is a somewhat archaic holdover from the early days of pickup trucks, when most manufacturers produced three sizes of trucks capable of hauling approximately those loads. Most modern pickups in any class can haul more than their weight class would imply, and can tow considerably more than their class when using a fifth-wheel hitch. One-ton pickups are considered Class 3 vehicles according to the federal Gross Vehicle Weight Classification system, and are often referred to as heavy-duty pickups alongside many three-quarter ton models.
The vast increase in payload of contemporary one-ton trucks over older models is largely due to the increased performance of modern engines, especially the turbocharged diesel engines common on one-ton trucks configured for maximum towing performance. Peak torque outputs of these engines are as high as 800 foot-pounds in the most powerful models. Improved structural strength and size and the use of dual rear tire or "dually" designs also helps to maximize the payload and towing capacity of modern one-ton trucks