Convert Bar to Atmosphere (bar → atm)

Converting bars to atmospheres is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in bars

   Start with the number of bars (bar) you want to convert.
2. 2
   Multiply by 0.986923

   The conversion factor from bar to atm is 0.986923. Multiply your value by this number.
3. 3
   Read the result in atmospheres

   The result is your value in atmospheres (atm).

Multiply the value in bars by 0.986923. For the reverse direction, multiply by 1.01325.

• ✓1 bar = 100 kPa = 0.987 atm = 14.5 psi.
• ✓Almost 1 atm — convenient approximation.
• ✓Tyre pressures: 2.0–2.5 bar typical car, 6–10 bar truck.

• ✗Assuming 1 bar = 1 atm exactly — 1.3% off.
• ✗Mixing bar with psi — need factor of 14.5.
• ✗Using bar for high-pressure work — switch to MPa.

What is the Bar?

The bar equals exactly 100,000 pascals (100 kPa) and is the everyday pressure unit in European tire pressures, hydraulic systems, and meteorology. The unit was chosen to be approximately equal to atmospheric pressure at sea level (1 bar = 0.987 atm). European cars have tire pressures of about 2.0–2.5 bar (29–36 psi), industrial hydraulic systems operate at 100–700 bar, and wine bottles are pressurized to about 6 bar internally for sparkling wines. Although technically not an SI unit, the bar is widely accepted for use with the SI system. Weather forecasts in some countries use 'millibar' (1 mbar = 1 hPa = 100 Pa) for atmospheric pressure. The bar relates to the pascal (100,000 Pa = 1 bar), the kilopascal (100 kPa = 1 bar), the psi (1 bar ≈ 14.504 psi), the atmosphere (1 atm ≈ 1.013 bar), and the mbar (1,000 mbar = 1 bar). It strikes a practical balance between scientific precision and everyday usefulness.

• European tyre pressure gauges
• Scuba-diving depth pressure
• Hydraulic and pneumatic systems

What is the Atmosphere?

The atmosphere equals exactly 101,325 pascals (the average atmospheric pressure at sea level, latitude 45°) and is a reference unit in chemistry, diving, and engineering. Defined for scientific convenience to represent 'standard atmospheric pressure,' it is widely used in chemistry (gas laws, reaction conditions), aviation (cabin pressure relative to ambient), and scuba diving (depth pressure: every 10 m of seawater adds about 1 atm). Standard reference conditions in chemistry often specify 1 atm and 25°C. The atmosphere relates to the pascal (101,325 Pa = 1 atm), the kilopascal (101.325 kPa = 1 atm), the bar (1.01325 bar = 1 atm), the psi (14.696 psi = 1 atm), the torr (760 torr = 1 atm), and the meter of seawater (10.33 mH₂O = 1 atm). The 'technical atmosphere' (1 at = 98.066 kPa = 1 kgf/cm²) is a slightly different historical unit no longer in use.

• Chemistry standard conditions
• Aviation cockpit pressurisation references
• Pressure tank and vessel ratings