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Technical Atmosphere to Bar Converter

Enter a pressure in technical atmospheres to convert to bar.

Result

4.9033 bar
71.12 psi

How it is calculated

The tool converts a pressure in technical atmospheres (at, equal to kgf/cm²) with two factors: bar = at × 0.980665 and psi = at × 14.2233. The bar value is shown with four decimals and the psi value with two. Negative numbers are not rejected: they are converted the same way, which is useful for vacuum or gauge readings below zero. The result is a pure unit conversion, so it keeps whatever reference the gauge uses; a gauge reading stays a gauge reading and is not turned into absolute pressure.

Worked example

An old boiler gauge reads 5 at and you want modern units. Bar: 5 × 0.980665 = 4.903325, which the tool rounds to 4.9033 bar. Psi: 5 × 14.2233 = 71.1165, shown as 71.12 psi. So 5 at is slightly less than 5 bar.

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Common mistakes

  • Treating 1 at as 1 atm or 1 bar. The technical atmosphere is 0.980665 bar, while a standard atmosphere is 1.01325 bar, so the three differ by a few percent.
  • Confusing at with atm when reading a nameplate; check whether it says kgf/cm² (at) or atm.
  • Assuming the answer is absolute pressure. Most gauges show gauge pressure, and the conversion does not add atmospheric pressure.
  • Using the rounded psi result for fine work: the psi is shown to two decimals only, so keep the bar value for further calculation.

About this calculator

The technical atmosphere (at) is an older metric pressure unit defined as exactly 1 kilogram-force per square centimetre (kgf/cm²), predating the SI pascal and bar. Because 1 kgf = 9.80665 N acting over 1 cm², 1 at = 98,066.5 Pa = 0.980665 bar — almost, but not quite, equal to a standard atmosphere (1 atm = 1.01325 bar).

The unit still shows up on older or Eastern-European-made pressure gauges, boiler and compressor nameplates, and hydraulic system specs, so mechanics and industrial technicians reading legacy equipment need to convert it to the bar or psi values used on modern instruments.

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