ISS facts
How high is the ISS?
The International Space Station orbits at an average altitude of about 400 kilometers (250 miles) above Earth's surface, in the region called low Earth orbit. Its exact height drifts between roughly 390 and 420 km — you can watch the current value live on the tracker map.
The altitude ladder: where 400 km sits
| Object | Altitude |
|---|---|
| Commercial jet cruise | 10–12 km |
| Kármán line (edge of space) | 100 km |
| ISS | ~400 km |
| Hubble Space Telescope | ~525 km |
| Starlink satellites | ~550 km |
| GPS satellites | ~20,200 km |
| Geostationary satellites | 35,786 km |
| The Moon | ~384,400 km |
For scale: if Earth were a basketball, the ISS would orbit less than a centimeter above its surface. "Space" is much closer than most people picture — the station is nearer to you than London is to Paris.
Why 400 km exactly?
The altitude is a compromise. Lower would mean more atmospheric drag and constant refueling to stay up; higher would put the station deeper into the Van Allen radiation belts and make every crew rotation and cargo flight more expensive, since visiting spacecraft need more energy to climb. Around 400 km, drag is manageable, radiation is acceptable, and Soyuz, Crew Dragon and cargo ships can reach it economically.
The ISS is always sinking
Even at 400 km a trace of atmosphere remains, and the station plows through it at 28,000 km/h. The resulting drag lowers its orbit by roughly two kilometers per month. Docked spacecraft periodically fire thrusters to "reboost" it back up — without these burns, the station would re-enter the atmosphere within a couple of years.
Can you see something 400 km away with the naked eye?
Easily — the ISS is the size of a football field, wrapped in highly reflective solar panels. When sunlight hits it against a dark sky it outshines every star. Find out if it's visible tonight, check pass times for your city, or learn how to spot it.