How Fast Does the ISS Orbit Earth? The Facts

Updated September 19, 2026 · 5 min read

The International Space Station travels at roughly 28,000 km/h — about 17,500 mph, or close to 7.7 km every single second. NASA quotes a round figure of about 17,500 mph (28,000 km/h) for the station’s speed, and it completes a lap of Earth in about 93 minutes, roughly 15.5 orbits a day.

That velocity has to be exactly right. At its altitude of about 400-420 km, the station must move sideways fast enough that the curved ground falls away beneath it at the same rate the station falls — which is what "being in orbit" actually means.

Speed at this altitude is fixed by physics

There is no choice in the matter. Orbital speed is set entirely by altitude: at any given height there is exactly one speed that keeps an object circling instead of falling back down or flying away. Slow down and gravity would drag the ISS back to Earth; speed up and it would climb to a higher, slower orbit.

At 400-420 km, gravity is only slightly weaker than at the surface — roughly 89% of surface gravity — so the station must still move astonishingly fast to stay up. The result is an orbital velocity of about 7.66 km/s, more than 20 times the speed of sound.

Putting that speed in context

These are rough figures for scale — very different objects with very different levels of "fast", but useful for judging the sheer pace of low Earth orbit.

A lap of Earth every hour and a half

At this speed the station covers the roughly 42,000 km of a full orbit in about 93 minutes — not 24 hours, the way Earth itself turns. Because the ISS is far inside the altitude where a geostationary satellite would sit, it laps the planet many times a day, which is why the crew sees about 16 sunrises and sunsets every 24 hours.

It is also why sighting opportunities come in runs: several passes over a few nights, then a gap while the ground track shifts west. The orbit explained page covers the geometry behind that pattern.

True speed vs how fast it moves across the sky

The station’s true velocity — seven-plus kilometres per second — is very different from what your eyes register, which is angular speed: how many degrees of the sky it crosses per second.

When it passes close to overhead, the ISS sweeps roughly one degree of sky every second, and the whole pass can take just a few minutes. Near the horizon, the same object at the same true speed looks like it’s crawling, because the path is foreshortened and farther from you. A single pass can look both "fast" overhead and "slow" at the ends — same real speed throughout.

This matters if you photograph it: for a camera, the station is a streak across the frame, and the exact rate depends on elevation. The photography guide works through it.

Is the speed constant?

Not exactly. The exact number drifts as the orbit changes. Atmospheric drag continuously lowers the orbit, and — counterintuitively — a lower orbit means a slightly higher orbital speed. Periodically the ISS performs reboost burns (usually with visiting vehicles) that raise it back up, lowering the speed again. So the readout on a live tracker wiggles within a range around 27,600 km/h.

Speed and altitude are two sides of the same coin — why a lower orbit is faster is explained on the how high is the ISS? page.

Sources and further reading

• NASA — Spot the Station FAQ (orbital speed)
• NASA — International Space Station Facts and Figures

Related

• How high is the ISS?
• The ISS orbit explained
• ISS live position & speed
• Why the ISS is visible at all
• How to read a pass prediction