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 pascal?
The pascal is the SI base unit of pressure, equal to one newton per square metre. It is used in meteorology, fluid dynamics, materials science, and all scientific pressure measurements.
Real-world uses
The pascal is the SI unit of pressure used in engineering stress analysis, materials science, and acoustics (sound pressure levels). Concrete and steel specifications list compressive strength in megapascals (MPa). Atmospheric pressure is about 101,325 Pa.
History
Named after Blaise Pascal, the French mathematician and physicist who conducted pioneering experiments on fluid pressure and vacuum in the 1640s. The pascal was adopted as the SI unit of pressure in 1971 at the 14th General Conference on Weights and Measures.
Common mistakes
Using pascals directly for everyday pressure is impractical since one pascal is a very small pressure (about the weight of a dollar bill spread over a desk). Most practical applications use kPa, hPa, or MPa instead.
When is this conversion used?
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 = 101,325 pascal
1 pascal = 1 pascal
How to convert atmosphere to pascal
To convert atmosphere to pascal, multiply the value by 101,325.
To convert pascal back to atmosphere, multiply by 0.00000987.
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 pascal
| atmosphere | pascal |
|---|---|
| 0.1 | 10,132.5 |
| 0.5 | 50,662.5 |
| 1 | 101,325 |
| 2 | 202,650 |
| 5 | 506,625 |
| 10 | 1,013,250 |
| 25 | 2,533,125 |
| 50 | 5,066,250 |
| 100 | 10,132,500 |
| 250 | 25,331,250 |
| 500 | 50,662,500 |
| 1,000 | 101,325,000 |
Common values
| atmosphere | pascal | |
|---|---|---|
| Car tyre | 2.17123119 atmosphere | 220,000 pascal |
| Standard atmosphere | 1 atmosphere | 101,325 pascal |
| Blood pressure (systolic) | 0.15790772 atmosphere | 16,000 pascal |
| Deep-sea submersible | 1,085.61559339 atmosphere | 110,000,000 pascal |
| Bicycle tyre | 6.11892425 atmosphere | 620,000 pascal |