Kilopound per Square Inch to Technical Atmosphere Converter

What is the difference between "at" and "atm"?

Different units! (Common source of confusion)

at (technical atmosphere):

• 1 at = 1 kgf/cm² = 98,066.5 Pa
• Engineering unit based on kilogram-force
• Symbol: at
• Historical European engineering

atm (standard atmosphere):

• 1 atm = 101,325 Pa (exactly, by definition)
• Based on sea-level atmospheric pressure
• Symbol: atm
• Scientific/meteorological standard

Relationship: 1 atm = 1.033 at (about 3% higher)

Why confusion?: Names sound similar, values close (both ≈ atmospheric pressure)

Technical Atmosphere to Atmosphere converter →

How do I convert at to bar?

Formula: bar = at × 0.980665

Quick approximation: 1 at ≈ 1 bar (1.9% difference)

Exact conversions:

• 1 at = 0.981 bar
• 2 at = 1.961 bar
• 5 at = 4.903 bar
• 10 at = 9.807 bar
• 100 at = 98.07 bar

Inverse: 1 bar = 1.0197 at

Why so close?: Bar defined (originally) to be close to atmospheric pressure, similar motivation as technical atmosphere

at to Bar converter →

How do I convert at to PSI?

Formula: PSI = at × 14.2233

Examples:

• 1 at = 14.22 PSI
• 2 at = 28.45 PSI
• 5 at = 71.12 PSI (typical air compressor)
• 10 at = 142.23 PSI
• 100 at = 1,422.33 PSI (high pressure)

Inverse: 1 PSI = 0.0703 at

Memory aid: 1 at ≈ 14 PSI

at to PSI converter →

How do I convert at to kPa or MPa?

Formula: kPa = at × 98.0665

Examples:

• 1 at = 98.07 kPa ≈ 0.1 MPa
• 5 at = 490.3 kPa ≈ 0.5 MPa
• 10 at = 980.7 kPa ≈ 1 MPa
• 50 at = 4,903 kPa ≈ 5 MPa
• 100 at = 9,807 kPa ≈ 10 MPa

Quick rule: Multiply by ~100 to get kPa, divide by ~10 to get MPa

at to kPa converter → at to MPa converter →

Why is this unit not used anymore?

SI adoption (1970s-1980s): Most countries transitioned to SI units (Pa, kPa, MPa, bar)

Problems with technical atmosphere:

• Not SI-compliant: Based on kilogram-force (gravitational unit)
• Ambiguity: "kg" is mass, not force (kgf needed for clarity)
• Gravity dependence: Assumes standard gravity (9.80665 m/s²)
• Confusion: Easy to confuse with standard atmosphere (atm)

Modern replacements:

• Bar: 1 at ≈ 1 bar (easy conversion)
• kPa: 1 at ≈ 100 kPa
• MPa: For high pressures (1 at = 0.1 MPa)

Still seen in:

• Older European equipment specifications
• Chinese industrial standards (some applications)
• Russian/former Soviet engineering documents
• Japanese industrial equipment (occasionally)
• Legacy pressure gauges and instruments

For new designs: Use bar, kPa, or MPa instead of at

Historical importance: Was convenient unit when bar not yet standardized, and provided easy mental approximation to atmospheric pressure.