Pressure Converter: psi, bar, kPa, atm
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1 bar = 14.50377 psiA person 1.75 m tall, on the same scale.
1 bar holds up a column of mercury 750.1 mm tall, or a column of water 10.2 m tall.
A pressure pushes a liquid up a tube until the weight of the column balances it. Torricelli's barometer does this with the pressure of the air and a tube that is empty at the top. Mercury is 13.6 times as dense as water, so its column is 13.6 times shorter. That is why a barometer uses mercury.
All Results
Quick Reference Table: Bar → Pounds per square inch
| Value (bar) | Result (psi) |
|---|---|
| 0.1 bar | 1.4504 psi |
| 0.5 bar | 7.2519 psi |
| 1 bar | 14.5038 psi |
| 2 bar | 29.0075 psi |
| 5 bar | 72.5189 psi |
| 10 bar | 145.0377 psi |
| 100 bar | 1, |
About Pressure Conversions
Pressure is force per unit of area. The pascal (Pa) is the SI unit of pressure, equal to one newton per square meter. One bar equals exactly 100,000 Pa and is common in weather forecasts and in industry. One standard atmosphere (atm) equals 101,325 Pa, about the air pressure at sea level. In the United States, PSI (pounds per square inch) is the usual unit for tire pressure, hydraulic systems and gas pressure. Blood pressure is measured in mmHg (millimeters of mercury). Normal air pressure at sea level is about 1,013.25 hPa.
Everyday Pressures
Tires, weather and the human body. Standard atmospheric pressure at sea level is 1,013.25 hPa, or 1 atm.
| Situation | bar | psi | kPa |
|---|---|---|---|
| Blood pressure (120 mmHg) | 0.16 | 2.32 | 16 |
| Everest summit | 0.337 | 4.888 | 33.7 |
| Atmosphere at sea level | 1.013 | 14.7 | 101.3 |
| Scuba diving at 10 m | 2.026 | 29.39 | 202.7 |
| Car tire | 2.2 | 31.91 | 220 |
| Champagne bottle | 6 | 87.02 | 600 |
| Road bicycle tire | 8 | 116 | 800 |
| Espresso machine | 9 | 130.5 | 900 |
History of pressure units
Pressure was first measured as a height: the column of mercury the air can hold up. That is why blood pressure is still given in millimeters of mercury, next to the pascal of the SI.
- In a letter to Michelangelo Ricci, Evangelista Torricelli described filling a glass tube with mercury and turning it upside down in a bowl: the column sank to about 70 cm and stayed there, held up by the weight of the air.
- At Blaise Pascal's request, his brother-in-law Florin Périer carried the experiment up the Puy de Dôme. The mercury column was shorter at the top: air pressure falls with height.
- The General Conference on Weights and Measures defined the standard atmosphere as 101,325 newtons per square meter.
- The newton per square meter, the SI unit of pressure, was given its own name: the pascal (Pa).
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