What was the payload capacity of the DUKW?

The DUKW had a payload capacity of 2.5 tons, or 5,000 pounds.

The American DUKW was an amphibious adaptation of the GMC CCKW 2½-ton six-wheel-drive truck. Its cargo rating was retained even though the vehicle gained a boat-shaped steel hull, a propeller and equipment for operating in surf and on beaches. It could carry supplies, ammunition and equipment over land, then continue through water to a beachhead.

The DUKW’s payload figure is also the source of the familiar “deuce-and-a-half” description associated with its truck family. Depending on the mission, the cargo space could instead carry roughly two dozen troops, although passenger loads and equipment affected the practical weight available.

The name DUKW is a GMC designation: D referred to the 1942 design year, U to utility, K to front-wheel drive and W to twin rear axles. More than 21,000 were built between 1942 and 1945, and the vehicle served in major Allied amphibious operations.