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Atmosphere (atm) - Unit Information & Conversion

Symbol:atm
Plural:atmospheres
Category:Pressure

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What is a Atmosphere?

Atmosphere (atm) equals average sea-level air pressure: 101,325 Pa = 14.696 PSI = 1.01325 bar. Standard unit in chemistry for gas laws, diving for depth pressure, engineering for high-pressure systems.

History of the Atmosphere

Defined in 1954 as exactly 101,325 pascals by CIPM. Based on average atmospheric pressure at sea level. Fundamental reference unit in gas laws (PV=nRT), thermodynamics, and scientific pressure measurements.

Quick Answer

What is an Atmosphere? Atmosphere (atm) = average air pressure at sea level = 101,325 Pa = 14.696 PSI = 1.01325 bar = 760 mmHg. Standard unit in chemistry (gas laws), diving (1 atm per 10m depth), physics. Sea level pressure varies 0.95-1.05 atm. Use our pressure converter for conversions.

Definition

1 atm = 101,325 Pa = 101.325 kPa = 14.696 PSI = 1.01325 bar = 760 mmHg = 760 Torr = 29.92 inHg

Common Uses

Chemistry: Gas laws (PV=nRT), reaction conditions, vapor pressures, standard conditions (STP). Diving: Depth pressure calculations (1 atm per 10m/33ft water). Physics: Standard reference pressure for equations, thermodynamics. Engineering: High-pressure systems, pressure vessels, gas storage.

Real-World Examples

Atmospheric Pressure Variations

  • Sea level (average): 1.000 atm = 101,325 Pa
  • High-pressure system: 1.035-1.050 atm = 1,048-1,064 hPa
  • Low-pressure system: 0.960-0.985 atm = 972-998 hPa
  • Hurricane eye: ~0.880-0.920 atm = 890-930 hPa
  • Strongest hurricane recorded: ~0.870 atm = 882 hPa
  • Denver (1 mile elevation): ~0.83 atm = 84 kPa
  • Mount Everest summit: ~0.337 atm = 34 kPa

Diving Pressure

  • Surface: 1 atm
  • 10m (33ft) depth: 2 atm total (1 atm water + 1 atm air)
  • 20m (66ft) depth: 3 atm total
  • 30m (99ft) depth: 4 atm total
  • 40m (131ft) recreational limit: 5 atm total
  • 130m (427ft) deep dive record: 14 atm total

Gas Cylinder Pressures

  • Scuba tank (full): 200-300 atm (3,000-4,500 PSI)
  • Compressed air (industrial): 7-10 atm (100-145 PSI)
  • Natural gas pipeline: 50-80 atm
  • Hydrogen fuel cell: 350-700 atm (5,000-10,000 PSI)
  • Laboratory gas cylinder: 150-200 atm
  • Helium balloon tank: 120-150 atm

Chemistry & Science

  • Standard Temperature and Pressure (STP): 1 atm, 0°C
  • Standard Ambient (SATP): 1 atm, 25°C
  • Autoclave sterilization: 1.5-2.0 atm (121-134°C)
  • Pressure cooker: 1.7-2.0 atm (115-121°C)
  • Vacuum pump (rough): 0.001-0.01 atm
  • High vacuum: 10^-6 to 10^-9 atm

Atmosphere Conversion Formulas

To Pascal:

1 atm = 101325 Pa
Example: 5 atmospheres = 506625 pascals

To Kilopascal:

1 atm = 101.325 kPa
Example: 5 atmospheres = 506.625 kilopascals

To Megapascal:

1 atm = 0.101325 MPa
Example: 5 atmospheres = 0.506625 megapascals

To Hectopascal:

1 atm = 1013.25 hPa
Example: 5 atmospheres = 5066.25 hectopascals

To Bar:

1 atm = 1.01325 bar
Example: 5 atmospheres = 5.06625 bars

To Millibar:

1 atm = 1013.25 mbar
Example: 5 atmospheres = 5066.25 millibars

To Technical Atmosphere:

1 atm = 1.033227 at
Example: 5 atmospheres = 5.166137 technical atmospheres

To Torr:

1 atm = 760 Torr
Example: 5 atmospheres = 3800 torr

To Millimeter of Mercury:

1 atm = 760 mmHg
Example: 5 atmospheres = 3800 millimeters of mercury

To Inch of Mercury:

1 atm = 29.921252 inHg
Example: 5 atmospheres = 149.606262 inches of mercury

To Pound per Square Inch:

1 atm = 14.695949 psi
Example: 5 atmospheres = 73.479744 pounds per square inch

To Kilopound per Square Inch:

1 atm = 0.014696 ksi
Example: 5 atmospheres = 0.07348 kilopounds per square inch

To Kilogram-force per Square Centimeter:

1 atm = 1.033227 kgf/cm²
Example: 5 atmospheres = 5.166137 kilograms-force per square centimeter

To Kilogram-force per Square Meter:

1 atm = 10332.274528 kgf/m²
Example: 5 atmospheres = 51661.37264 kilograms-force per square meter

To Millimeter of Water Column:

1 atm = 10332.274528 mmH₂O
Example: 5 atmospheres = 51661.37264 millimeters of water column

To Inch of Water Column:

1 atm = 406.782464 inH₂O
Example: 5 atmospheres = 2033.912322 inches of water column

Frequently Asked Questions

1 atm = 14.696 PSI (often rounded to 14.7 PSI) Examples:

  • 2 atm = 29.4 PSI (10m dive depth)
  • 3 atm = 44.1 PSI (20m dive depth)
  • 10 atm = 147 PSI (compressed air)
  • 100 atm = 1,470 PSI (gas cylinder) Atmosphere to PSI converter →

Convert Atmosphere

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Atmosphere Quick Info

atm
Symbol:atm
Category:Pressure
System:Various
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