HesapHanem

Bar to Atm Converter

Enter a pressure in bar to convert to atm, psi and kPa.

How it is calculated

The tool multiplies the pressure in bar by fixed factors: atm = bar × 0.98692327, psi = bar × 14.5037738 and kPa = bar × 100. Atmospheres are shown with four decimals and psi and kPa with two. A standard atmosphere is defined as 1.01325 bar, which is where 0.98692327 (the inverse of 1.01325) comes from. The tool converts the number you type and does not know whether it is a gauge reading (relative to the air around you) or an absolute pressure; the factors work the same for both, but the meaning differs. Zero and negative values are converted without complaint, which is useful for vacuum readings on a gauge.

Worked example

A tyre or vessel is marked 2.5 bar. Step 1: atm = 2.5 × 0.98692327 = 2.4673, shown as 2.4673 atm. Step 2: psi = 2.5 × 14.5037738 = 36.26 psi. Step 3: kPa = 2.5 × 100 = 250.00 kPa. So 2.5 bar is about 2.47 atmospheres, 36 psi or 250 kilopascals.

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Common mistakes

  • Treating bar and atm as equal: 1 atm is 1.01325 bar, so the difference is about 1.3%, which matters for precise work.
  • Mixing up gauge and absolute pressure: a gauge reading of 2.5 bar is about 3.5 bar absolute at sea level.
  • Confusing bar with millibar (mbar) or with kPa; 1 bar is 1000 mbar and 100 kPa.
  • Dividing instead of multiplying when converting from atm back to bar; this tool goes bar to atm only.
  • Rounding the psi figure too early before using it in a further calculation.

Sources

About this calculator

This calculator converts pressure from bar — a metric unit close to normal atmospheric pressure and defined as exactly 100,000 pascals — into standard atmospheres (1 atm = 1.01325 bar), psi (1 bar ≈ 14.5038 psi) and kilopascals (1 bar = 100 kPa) in one step.

Bar is common in European gauges, tire pressure specs and diving equipment, while atm and psi dominate in scientific literature and North American engineering respectively — this converter bridges the three unit systems engineers, divers and technicians run into daily.

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Comments (1)

  • Editorial team

    For a quick reference point, enter 1.01325: the tool returns 1.0000 atm and about 14.70 psi, which is standard sea-level pressure. Another real example is an espresso machine rated at 9 bar, which is about 8.88 atm or 130.53 psi. Weather reports in hPa or mbar are 1000 times smaller than bar, so divide by 1000 first. Which gauge or device are you converting for?

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