What is the internal atmospheric pressure of the ISS in kilopascals?

The internal atmospheric pressure of the ISS is 101.3 kilopascals.

That pressure is approximately one atmosphere, or 14.7 pounds per square inch, making the station’s cabin pressure broadly equivalent to sea-level pressure on Earth. The ISS uses an Earth-like nitrogen-oxygen atmosphere rather than the low-pressure pure-oxygen environment used in some early crewed spacecraft.

Maintaining the correct pressure is essential for more than breathing. It supports comfortable long-duration living and provides the pressure conditions required by station equipment, seals, cooling systems, and scientific hardware. The Environmental Control and Life Support System continually manages cabin composition, humidity, carbon dioxide, trace contaminants, and oxygen supply.

The figure is often confused with oxygen percentage. Oxygen makes up about 21% of the ISS atmosphere, while nitrogen accounts for roughly 79%; 101.3 kPa describes the total pressure of the mixed atmosphere. Spacewalks require a separate procedure: astronauts enter an airlock, lower its pressure, and breathe a suit atmosphere before opening the outer hatch.