Pressure Converter
Convert pascals, bar, psi, atmospheres and torr.
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About Pressure
Pressure covers six units and each one belongs to a different profession. Pascals and kilopascals are the SI units, used in science, engineering and in tyre pressure specs in much of the world. Bars are common in European industry, diving and car tyres. PSI is the everyday unit in the United States and appears on air compressors, tyre gauges and hydraulic gear. Atmospheres give a convenient reference against air pressure at sea level and turn up in chemistry and diving. Torr is the unit of vacuum work and lab equipment. Visitors arrive here to inflate a tyre from a spec quoted in the wrong unit, read a barometer or weather report, size a pump, or work through a gas-law problem. The pages used most are bar to psi, psi to bar, kilopascals to psi and pascals to bar.
The orientation worth having is that pressure is force spread over an area, which is why every unit here can be traced back to a force and a surface. That also explains why the pascal, the SI unit, is a small quantity: it is one unit of force over a fairly large area, so real-world pressures produce big pascal numbers and people reach for kilopascals or bar instead. The genuine gotcha in this category is gauge versus absolute pressure. A tyre gauge reads zero when the tyre is flat, but the tyre is not actually at zero pressure, it is at atmospheric pressure. That reading is gauge pressure, measured relative to the air around you. Absolute pressure counts up from a true vacuum instead, and the difference between the two is roughly one atmosphere. Converting between units never changes which of the two you have, so if a spec is gauge and you compare it against an absolute figure you will be out by around an atmosphere regardless of how carefully you convert. Always check which kind your source means before trusting the comparison.
Every pair page shows the formula used, a worked example, and a reference table of common values such as typical tyre and atmospheric pressures. All of it is free, no account or sign-up is needed, and the calculation runs inside your browser so nothing you enter is uploaded. If you need the underlying force rather than the pressure, the force converter is the companion hub.
Frequently asked questions
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the surrounding air, which is why a tyre gauge reads zero on a flat tyre even though the tyre still contains air at atmospheric pressure. Absolute pressure is measured from a true vacuum, so it includes that atmosphere. The two differ by roughly one atmosphere. Unit conversion does not change which kind you have, so check what your source means before comparing figures.
Which unit should I use for tyre pressure?
It depends where you are. US gauges and specs use psi, while much of Europe uses bar and many manufacturers quote kilopascals. All three describe the same thing, so the right approach is to convert the manufacturer figure into whatever your gauge reads rather than guessing. The bar to psi and kilopascals to psi pages are the two people use most for this.
Why is the pascal such a small unit?
Because pressure is force divided by area, and the pascal is defined as one newton spread over a square meter, which is a large area for a small force. Real pressures therefore come out as very large pascal numbers, which is inconvenient to read. That is why people use kilopascals, bar or atmospheres in practice, and why the pascal itself mostly appears in formulas rather than on gauges.
What is a torr used for?
Torr is the traditional unit of vacuum measurement and still appears throughout laboratory equipment, vacuum pumps and scientific instrumentation. It is convenient at very low pressures, where bar and atmosphere values become awkward decimals. If you are reading a vacuum gauge or a piece of lab documentation you will meet it; outside that world it is rare.