Scientific

Standard Atmosphere

Definition

A reference unit of pressure defined as exactly 101,325 pascals (101.325 kPa), representing the approximate mean atmospheric pressure at sea level.

Explanation

Standard atmosphere (atm) is used to define other pressure units: 1 atm = 760 mmHg = 14.696 psi = 1.01325 bar. A typical car tire is inflated to 2.2–2.5 atm gauge pressure (above atmospheric). Deep-sea submersibles must withstand more than 1,000 atm at 10 km depth. The standard atmosphere is also the upper boundary of ‘Standard Conditions’ in gas law calculations.

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