420 t926,000 lb
The International Space Station has a mass of about 420 tonnes (around 925,000 lb). NASA’s official figure is 419,725 kg, for the station itself. Crew and cargo spacecraft docked to it can push the total past 450 tonnes. In orbit it floats, so this is its mass: what it would weigh on Earth.
| With docked spacecraft, December 2021Station plus the crew and cargo vehicles attached at the time | 459 t1,010,000 lb |
|---|---|
| NASA deorbit planning figure, 2024Given as “more than” 430,000 kg | 430 t948,000 lb |
| Station alone, todayNASA’s official figure | 420 t925,000 lb |
| After the Destiny lab arrived, February 2001ESA: “over 100 tonnes” | 100 t220,000 lb |
| First module, Zarya, 1998Including 3,800 kg of propellant | 19.3 t42,600 lb |
Strictly speaking, the ISS weighs almost nothing on its own scales. Gravity is still about 90% as strong up there as on the ground, but the station and everything in it are in free fall, moving sideways at about 17,500 mph (28,000 km/h) so they keep falling around the Earth instead of into it. That is why astronauts float.
So when NASA gives the station as 419,725 kg, it means its mass: how much stuff it is made of. Bring it down to the ground in one piece and that is what it would weigh, about 420 tonnes or 925,335 lb.
No rocket could launch the ISS in one go. The first module, Russia’s Zarya, went up on a Proton rocket on 20 November 1998 and had a mass of 19,323 kg (42,600 lb). About two weeks later the Space Shuttle Endeavour attached the US Unity node to it. When the US Destiny laboratory arrived in February 2001, the station passed 100 tonnes.
NASA counts 42 assembly flights in all: 37 on the Space Shuttle and five on Russian Proton and Soyuz rockets. Putting the pieces together took 161 spacewalks over 13 years, and the last shuttle delivery came in May 2011. Russia added the Nauka laboratory and the Prichal docking node in 2021.
The result is 109 m (356 ft) from end to end, one yard short of an American football field including the end zones. It has 1,005 m³ of pressurised volume, of which 388 m³ is living space.
The station is never quite the same mass two days running. Crew capsules and cargo ships come and go, and while they are docked they add to the total. Guinness World Records put the station at 418,190 kg on 22 December 2021, rising to 459,025 kg (1,011,976 lb) with the visiting spacecraft attached that day, about 41 tonnes more.
Supplies get eaten, water and propellant get used, and departing cargo ships carry rubbish away to burn up in the atmosphere. That is why figures from different sources and years range from about 418 to 430 tonnes for the station alone. The game uses the round 420 tonnes.
The ISS is due to retire around 2030. At its height of about 415 km (257 miles), thin air drags on it constantly, and without regular boosts it would fall back to Earth within one or two years. Left uncontrolled, a structure this heavy would scatter large pieces over a wide area, so NASA has ruled that out.
Instead, NASA paid SpaceX up to $843 million to build the US Deorbit Vehicle, a spacecraft that will steer the empty station down into a remote, uninhabited part of the ocean. The station is expected to break apart on the way down, and whatever survives will sink to the sea floor. NASA also looked at cutting it apart and bringing modules home, but nothing flying today has the space shuttle’s cargo bay to carry them.
NASA puts it at 925,335 lb (419,725 kg). With crew and cargo spacecraft docked, it can pass a million pounds: Guinness recorded 1,011,976 lb in December 2021.
It is 109 m (356 ft) from end to end, just one yard short of an American football field with its end zones. The main truss alone is 94 m (310 ft) long.
Gravity at the station’s height is about 90% of what it is on the ground. Astronauts float because they and the station are falling around the Earth together at the same rate, so nothing presses them against the floor.
NASA counts 42 assembly flights: 37 Space Shuttle missions and five Russian Proton and Soyuz launches, plus 161 spacewalks to connect everything. More modules have been added since.
Yes, by a wide margin. Tiangong, completed in 2022, is about 100 tonnes, roughly a quarter of the ISS. Guinness lists the ISS as the largest space station ever built.
Last checked October 2, 2026.
