Pressure Converter
Convert psi to bar, kPa and atmospheres — plus Pascals, mbar and mmHg — instantly. Type any value to update every field at once.
- 1 psi = 0.0689476 bar; 1 bar = 14.5038 psi. Multiply psi by 0.0689 for bar.
- 1 atm = 101,325 Pa = 1.01325 bar = 14.696 psi = 760 mmHg. The sea-level reference pressure.
- Car tyres: 28–36 psi (1.9–2.5 bar). Check the door-jamb sticker; set them cold.
- 1 mbar = 1 hPa = 100 Pa. Weather pressure is quoted in millibars; sea level is 1,013.25 mbar.
- 1 bar = 100,000 Pa = 100 kPa. Close to, but not exactly, one atmosphere.
| Pressure | Pa | bar | psi | atm |
|---|---|---|---|---|
| Standard atmosphere | 101,325 | 1.01325 | 14.696 | 1 |
| Car tyre (typical, 30 psi) | 206,843 | 2.069 | 30 | 2.041 |
| Bicycle tyre (80 psi) | 551,581 | 5.516 | 80 | 5.443 |
| 1 bar | 100,000 | 1 | 14.504 | 0.9869 |
| Deep sea (1,000 m) | 10,132,500 | 101.33 | 1,469.6 | 100 |
How do you convert psi to bar?
1 psi equals 0.0689476 bar, so multiply psi by 0.0689 to get bar, or multiply bar by 14.5038 to go the other way. So 30 psi — a typical UK car tyre pressure — is about 2.07 bar, and 100 psi is 6.89 bar. Both units appear on UK garage air lines and tyre placards, which is why psi-to-bar is the pressure conversion drivers reach for most. As a worked example you can check against the tool, type 30 into the PSI field: the converter returns 2.0684271 bar, 206.84271 kPa, 2.04137883 atm and 206,843 Pa.
Pressure is force spread over an area — 1 Pascal is 1 Newton per square metre — so the psi and bar figures both describe how hard the air inside a tyre pushes on every part of its inner surface. To work with the force behind that pressure, use the force converter; for the closely related quantity of mechanical stress in solids, see the stress converter.
What is standard atmospheric pressure in every unit?
Standard atmospheric pressure (1 atm) equals 101,325 Pa, which is 101.325 kPa, 1.01325 bar, 14.696 psi or 760 mmHg. This is the agreed sea-level reference used in chemistry, physics and aviation, and it is roughly the weight of the whole column of air above one square metre of ground. Note that 1 bar (100,000 Pa) is close to, but not exactly, one atmosphere — a small difference that matters in precise scientific work but not when pumping up a tyre.
What tyre pressure should my UK car run at?
Most UK passenger cars run at 28–36 psi (1.9–2.5 bar), but the correct figures for your car are on a sticker inside the driver's door jamb or fuel-filler flap, and in the handbook. Front and rear pressures often differ, and fully loaded journeys usually need higher pressures, so it is worth reading the placard rather than guessing. Always check pressures when the tyres are cold, because driving warms the air and raises the reading by a couple of psi.
What unit does UK weather forecasting use?
The UK Met Office quotes atmospheric pressure in millibars (mbar), which are identical to hectopascals — 1 mbar = 1 hPa = 100 Pa. Standard sea-level pressure is 1,013.25 mbar; readings below about 1,000 mbar usually mean unsettled, wet weather, while above roughly 1,020 mbar brings settled, calm conditions. A deep Atlantic low can drop below 950 mbar, which is what drives the strongest UK storms.
What is the difference between gauge and absolute pressure?
Absolute pressure is measured from a perfect vacuum, while gauge pressure is measured relative to atmospheric pressure — so atmospheric pressure reads zero on a gauge. Tyre and most other everyday pressures are gauge pressures: a tyre "at 2.0 bar" actually holds about 3.01 bar of absolute pressure, because the 1.01 bar of atmosphere is already pressing on everything before you start pumping. The distinction is usually written as barg or psig (gauge) versus bara or psia (absolute).
This matters whenever a calculation crosses between the two conventions, such as comparing a vacuum reading to a boiler rating, or feeding a gauge value into a gas-law formula that expects absolute pressure. The converter above works on the raw numbers, so add or subtract one atmosphere (about 14.7 psi or 1.013 bar) yourself when you need to switch between gauge and absolute.
Pressure conversion FAQs
1 psi equals 0.0689476 bar, so multiply psi by 0.0689 to get bar. To go the other way, 1 bar = 14.5038 psi. For example, 30 psi (a typical car tyre) is about 2.07 bar, and 100 psi is 6.89 bar.
Standard atmospheric pressure (1 atm) equals 101,325 Pa, 101.325 kPa, 1.01325 bar, 14.696 psi or 760 mmHg. It is the sea-level reference pressure used across science, engineering and aviation.
Most UK cars run at 28–36 psi (1.9–2.5 bar), but check the sticker inside the driver's door jamb or the handbook for your exact figures. Front and rear differ, and loaded journeys need more. Always check when tyres are cold.
The Met Office uses millibars (mbar), which are identical to hectopascals (1 mbar = 1 hPa = 100 Pa). Standard sea-level pressure is 1,013.25 mbar; below about 1,000 mbar brings unsettled weather, above 1,020 mbar settled.
Absolute pressure is measured from a perfect vacuum; gauge pressure is measured relative to atmospheric pressure. Tyre pressures are gauge pressures, so 2.0 bar gauge means 2.0 bar above atmospheric, or about 3.01 bar absolute.
A millibar equals 100 Pa, or 0.001 bar, and is the standard unit in UK weather forecasting. Sea-level pressure is 1,013.25 mbar; a deep low can fall below 950 mbar, while high pressure can exceed 1,040 mbar.
Multiply kilopascals by 0.145038 to get psi. So 220 kPa (a common tyre placard value) is about 31.9 psi. Many car tyre placards list pressures in kPa as well as bar and psi, so this conversion is handy at the garage.
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