What is bar?
A bar is a pressure unit approximately equal to standard atmospheric pressure, or 100,000 pascals. It is widely used in meteorology, hydraulics, diving equipment, and industrial pressure gauges.
Real-world uses
Bars are widely used in European tyre pressure specifications, compressed gas cylinder ratings, scuba diving depth gauges, and industrial process controls. Espresso machines operate at 9–15 bar. Atmospheric pressure is approximately 1.013 bar.
History
The bar was introduced by Norwegian meteorologist Vilhelm Bjerknes in 1909, derived from the Greek word "baros" meaning weight. Though not an SI unit, it is widely accepted in industry and was retained in the EU Directive on units of measurement.
Common mistakes
Confusing bar with atm—they are close (1 atm ≈ 1.01325 bar) but not identical. Also, gauge pressure (barg) versus absolute pressure (bara) is often mixed up; gauge pressure reads zero at atmospheric pressure.
What is kilopascal?
A kilopascal is a metric pressure unit equal to 1,000 pascals. It is used for weather forecasts, tire pressure specifications in metric countries, and structural and mechanical engineering calculations.
Real-world uses
Kilopascals are used for tyre pressure in most countries (standard car tyres are about 200–250 kPa), blood pressure in some medical systems, and hydraulic system specifications. Atmospheric pressure at sea level is approximately 101.325 kPa.
History
The kilopascal became a practical engineering unit with the adoption of the SI system. It offers a convenient scale for everyday pressure measurements, bridging the gap between the tiny pascal and the larger bar or atmosphere.
Common mistakes
Confusing kPa with psi when checking tyre pressure. 1 psi ≈ 6.895 kPa, so 32 psi ≈ 220 kPa. Inflating a tyre to 32 kPa instead of 220 kPa would leave it nearly flat.
When is this conversion used?
Tyre pressure gauges, HVAC systems, and industrial equipment may use different pressure units depending on the manufacturer and region. Converting between psi, bar, and kPa is common in automotive and engineering work.
Worked examples
1 bar = 100 kilopascal
1 kilopascal = 1,000 pascal
How to convert bar to kilopascal
To convert bar to kilopascal, multiply the value by 100.
To convert kilopascal back to bar, multiply by 0.01.
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
Quick reference: bar to kilopascal
| bar | kilopascal |
|---|---|
| 0.1 | 10 |
| 0.5 | 50 |
| 1 | 100 |
| 2 | 200 |
| 5 | 500 |
| 10 | 1,000 |
| 25 | 2,500 |
| 50 | 5,000 |
| 100 | 10,000 |
| 250 | 25,000 |
| 500 | 50,000 |
| 1,000 | 100,000 |
Common values
| bar | kilopascal | |
|---|---|---|
| Car tyre | 2.2 bar | 220 kilopascal |
| Standard atmosphere | 1.01325 bar | 101.325 kilopascal |
| Blood pressure (systolic) | 0.16 bar | 16 kilopascal |
| Deep-sea submersible | 1,100 bar | 110,000 kilopascal |
| Bicycle tyre | 6.2 bar | 620 kilopascal |