The International Space Station has an approximate mass of 420 metric tons. NASA lists its mass at about 419,725 kilograms, which rounds to roughly 420,000 kilograms or 420 metric tons.
That figure represents the assembled orbital complex, including its pressurized modules, trusses, solar arrays, laboratories, robotic systems and other permanent hardware. The exact mass can vary as visiting spacecraft, cargo ships, fuel, water and experiment equipment arrive or depart.
The ISS reached its modern scale through construction in orbit. Major contributions came from NASA, Roscosmos, the European Space Agency, Japan’s JAXA and Canada’s space agency. Modules and truss segments were launched separately and joined over many years.
A common mix-up is confusing the station’s mass with its length or with the mass of a single module. The ISS stretches roughly 109 meters across its largest dimensions, while individual components weigh only a fraction of the completed station. Its mass also exceeds 400 metric tons even though it remains in low Earth orbit.