What is atmosphere?
An atmosphere (atm) is a pressure unit equal to mean atmospheric pressure at sea level, approximately 101,325 pascals. It is used as a reference in chemistry, diving tables, and altitude calculations.
Real-world uses
Atmospheres are used as a reference pressure in chemistry (standard conditions: 1 atm, 25°C), scuba diving (each 10 m of seawater adds about 1 atm), and high-pressure industrial applications like autoclaves and pressure vessels.
History
The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at 0°C under standard gravity. Evangelista Torricelli first measured atmospheric pressure in 1644 using a mercury barometer, establishing this foundational concept.
Common mistakes
Confusing standard atmosphere (101,325 Pa) with technical atmosphere (1 kgf/cm² ≈ 98,066.5 Pa). Also, assuming atmospheric pressure is constant at 1 atm everywhere—it varies with altitude, weather, and temperature.
What is pound per square inch?
Pound per square inch (psi) is an imperial pressure unit widely used in the United States for tire inflation, hydraulic system pressures, gas cylinder ratings, and plumbing specifications.
Real-world uses
PSI is the standard pressure unit in the United States for tyre inflation (typically 30–35 psi for cars), compressed air tools, hydraulic systems, and water pressure. HVAC systems, fire extinguisher ratings, and pressure cooker specifications use psi in North America.
History
Pounds per square inch emerged naturally from the Imperial/US customary system, combining the pound-force with the square inch. It became the dominant pressure unit in American industry and remains deeply embedded in US engineering standards and building codes.
Common mistakes
Not distinguishing between psi (absolute, psia) and psig (gauge, relative to atmosphere). A tyre reading of 32 psig actually means about 46.7 psia. Also, confusing psi with kPa when using equipment from metric countries.
When is this conversion used?
Converting between atmosphere and pound per square inch is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Tyre pressure gauges, HVAC systems, and industrial equipment may use different pressure units depending on the manufacturer and region. Converting between psi, bar, and kPa is common in automotive and engineering work.
Worked examples
1 atmosphere = 14.69594878 pound per square inch
1 pound per square inch = 6,894.75729317 pascal
How to convert atmosphere to pound per square inch
To convert atmosphere to pound per square inch, multiply the value by 14.69594878.
To convert pound per square inch back to atmosphere, multiply by 0.06804596.
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
Quick reference: atmosphere to pound per square inch
| atmosphere | pound per square inch |
|---|---|
| 0.1 | 1.46959488 |
| 0.5 | 7.34797439 |
| 1 | 14.69594878 |
| 2 | 29.39189755 |
| 5 | 73.47974388 |
| 10 | 146.95948776 |
| 25 | 367.39871939 |
| 50 | 734.79743878 |
| 100 | 1,469.59487755 |
| 250 | 3,673.98719388 |
| 500 | 7,347.97438776 |
| 1,000 | 14,695.94877551 |
Common values
| atmosphere | pound per square inch | |
|---|---|---|
| Car tyre | 2.17123119 atmosphere | 31.9083023 pound per square inch |
| Standard atmosphere | 1 atmosphere | 14.69594878 pound per square inch |
| Blood pressure (systolic) | 0.15790772 atmosphere | 2.3206038 pound per square inch |
| Deep-sea submersible | 1,085.61559339 atmosphere | 15,954.15115032 pound per square inch |
| Bicycle tyre | 6.11892425 atmosphere | 89.92339739 pound per square inch |