Understanding technical atmospheres to standard atmospheres Conversion
The technical atmosphere (at) equals one kilogram-force per square centimetre (98,066.5 Pa), a metric engineering unit. The standard atmosphere (atm) is defined as exactly 101,325 Pa, representing average sea-level air pressure and serving as a reference in chemistry and physics. Because the two units are close but not identical, converting between them prevents subtle errors when comparing metric gauge pressures against physical standard-atmosphere references.
Conversion Formula
To convert technical atmospheres to standard atmospheres, multiply by this factor:
Step-by-Step Example
Convert 25 technical atmospheres to standard atmospheres.
How to Convert technical atmospheres to standard atmospheres
Apply the fixed ratio between the two atmosphere definitions to convert.
- Note the factor: One technical atmosphere equals 0.9678411 standard atmospheres.
- Multiply: Multiply your value in at by 0.9678411.
- Work the example: For 25 at, compute 25 × 0.9678411.
- Read the result: The answer is 24.1960 atm.
technical atmospheres to standard atmospheres conversion table
| technical atmospheres (at) | standard atmospheres (atm) |
|---|---|
| 0 | 0 |
| 1 | 0.9678411 |
| 2 | 1.935682 |
| 3 | 2.903523 |
| 4 | 3.871364 |
| 5 | 4.839206 |
| 6 | 5.807047 |
| 7 | 6.774888 |
| 8 | 7.742729 |
| 9 | 8.71057 |
| 10 | 9.678411 |
| 15 | 14.51762 |
| 20 | 19.35682 |
| 25 | 24.19603 |
| 30 | 29.03523 |
| 40 | 38.71364 |
| 50 | 48.39206 |
| 60 | 58.07047 |
| 70 | 67.74888 |
| 80 | 77.42729 |
| 90 | 87.1057 |
| 100 | 96.78411 |
| 150 | 145.1762 |
| 200 | 193.5682 |
| 250 | 241.9603 |
| 300 | 290.3523 |
| 400 | 387.1364 |
| 500 | 483.9206 |
| 600 | 580.7047 |
| 700 | 677.4888 |
| 800 | 774.2729 |
| 900 | 871.057 |
| 1000 | 967.8411 |
| 2000 | 1935.682 |
| 3000 | 2903.523 |
| 4000 | 3871.364 |
| 5000 | 4839.206 |
| 10000 | 9678.411 |
| 25000 | 24196.03 |
| 50000 | 48392.06 |
| 100000 | 96784.11 |
| 250000 | 241960.3 |
| 500000 | 483920.6 |
| 1000000 | 967841.1 |
What is the technical atmosphere?
The technical atmosphere (at) is a non-SI unit of pressure equal to one kilogram-force per square centimeter. It was widely used in engineering, especially in Europe, before the pascal became standard.
Definition
The technical atmosphere is defined as the pressure of one kilogram-force acting on one square centimeter:
This equals exactly 1 kgf/cm² (98,066.5 Pa), because standard gravity is 9.80665 m/s². It is close to, but distinct from, the standard atmosphere (atm = 101,325 Pa) and the bar (100,000 Pa).
Origin and History
The technical atmosphere arose from the gravitational metric system of units, which used the kilogram-force rather than the newton. Expressing pressure as kilogram-force per square centimeter was intuitive for engineers weighing loads, and the unit became common in mechanical and hydraulic engineering, boilers, and pneumatics through much of the 20th century.
Law and Notable Facts
The technical atmosphere is not part of the SI and its use is discouraged in favor of the pascal or bar. It is easily confused with the standard atmosphere; the two differ by about 3.3%. Gauge and absolute variants were often written "atü" (gauge) and "ata" (absolute) in German-language engineering.
Real-World Examples and Conversions
- 1 at = 1 kgf/cm² = 98.0665 kPa ≈ 0.9678 atm.
- 1 at ≈ 14.223 psi, close to but slightly below the 14.696 psi of one standard atmosphere.
- A pressure of 10 at (about 981 kPa) is a common rating benchmark for industrial hydraulic components.
- 1 at ≈ 0.980665 bar, so the bar and technical atmosphere differ by under 2%.
What is the standard atmosphere?
The standard atmosphere (atm) is a unit of pressure defined as a fixed reference value close to the average atmospheric pressure at sea level. It is widely used in chemistry, physics, engineering, and diving to express pressures relative to typical sea-level conditions.
Definition
The standard atmosphere is defined exactly as 101,325 pascals:
This is equivalent to 1013.25 hectopascals (millibars), 760 millimeters of mercury (torr), and about 14.6959 pounds per square inch. The value was fixed by the 10th General Conference on Weights and Measures (CGPM) in 1954.
Origin and History
Early pressure measurement grew from Evangelista Torricelli's 1643 barometer experiments, which showed the atmosphere supports a mercury column about 760 mm high. The "atmosphere" became a convenient reference for a whole unit of ambient pressure. In 1954 the CGPM adopted the exact value 101,325 Pa, based on a 760 mm mercury column at 0 °C under standard gravity, to remove the temperature and location dependence of earlier definitions.
Law and Notable Facts
The standard atmosphere is accepted for use with the SI but is not an SI unit; the SI unit of pressure is the pascal. IUPAC now recommends the bar (100,000 Pa) rather than the atmosphere as the standard pressure for reporting thermodynamic data, though "atm" remains common. Note that the technical atmosphere (at) is a different unit equal to 98,066.5 Pa.
Real-World Examples and Conversions
- Average sea-level air pressure is very close to 1 atm (101.325 kPa).
- Ocean pressure increases by roughly 1 atm for every 10 meters of seawater depth, so a diver at 30 m experiences about 4 atm total.
- A typical car tire inflated to 32 psi holds about 2.2 atm of gauge pressure.
- The pressure inside a champagne bottle is roughly 6 atm (about 608 kPa).
Frequently Asked Questions
Are technical and standard atmospheres the same?
No. One technical atmosphere is about 0.967841 standard atmospheres because they use different definitions (98,066.5 Pa versus 101,325 Pa).
How do I convert standard atmospheres back to technical atmospheres?
Multiply the atm value by 1.033227, or divide by 0.9678411.
Which is larger, a technical or a standard atmosphere?
The standard atmosphere is larger; a technical atmosphere is roughly 3.2% smaller.
Why do both units exist?
The standard atmosphere models real sea-level air pressure, while the technical atmosphere was chosen for convenient metric engineering (1 kgf/cm²).
What is 10 technical atmospheres in standard atmospheres?
Multiply 10 by 0.9678411 to get about 9.678 atm.
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Complete technical atmospheres conversion table
| Unit | Result |
|---|---|
| pascals (Pa) | 98066.5 Pa |
| kilopascals (kPa) | 98.0665 kPa |
| megapascals (MPa) | 0.0980665 MPa |
| hectopascals (hPa) | 980.665 hPa |
| millibar (mbar) | 980.665 mbar |
| bar (bar) | 0.980665 bar |
| torr (torr) | 735.5592 torr |
| meters of water @ 4°C (mH2O) | 10 mH2O |
| millimeters of mercury (mmHg) | 735.5591 mmHg |
| standard atmospheres (atm) | 0.9678411 atm |
| centimeters of water (cmH2O) | 1000 cmH2O |
| centimeters of mercury (cmHg) | 73.55591 cmHg |
| pounds per square inch (psi) | 14.22334 psi |
| kilopound per square inch (ksi) | 0.01422334 ksi |
| Inches of mercury (inHg) | 28.95902 inHg |