Pressure Converter

Pressure converter for weather, tires, and engineering — psi, bar, and atmospheres.

Convert between pascals, kilopascals, bar, psi, atmospheres, torr and mmHg. Use it for tyre pressure, weather, blood pressure, compressors, boilers and diving.

Popular Pressure Conversions

• Bar to Pounds per Square Inch
• Pounds per Square Inch to Bar
• Pounds per Square Inch to Kilopascal
• Kilopascal to Pounds per Square Inch
• Atmosphere to Pounds per Square Inch
• Atmosphere to Bar
• Millimeter of Mercury to Kilopascal
• Bar to Kilopascal
• Bar to Pascal
• Pounds per Square Inch to Pascal

All Pressure Units

How pressure conversion works

Pressure is force per unit area. The SI unit is the pascal (Pa), equal to one newton per square metre. All other units here are defined from it:

bar to psi: multiply by 14.5038. psi to bar: multiply by 0.0689476. psi to kPa: multiply by 6.894757. kPa to psi: multiply by 0.145038. mmHg to kPa: multiply by 0.133322.

Tyre pressure chart: psi to bar

Most passenger cars specify roughly 30–35 psi (2.1–2.4 bar), but always use the figure on the sticker inside the driver's door or in the owner's manual. Check pressure when tyres are cold.

Blood pressure and weather

• Blood pressure is measured in mmHg. A reading of 120/80 mmHg is 16/10.7 kPa. Some countries report kPa, but Pakistan and the US use mmHg.
• Atmospheric pressure at sea level is 1 atm = 101.325 kPa = 1,013.25 hPa (millibar). Weather maps use hPa or mbar (1 hPa = 100 Pa). Pressure falls with altitude: by roughly 1.2 kPa for every 100 m of climb near sea level.

Where each unit is used

• psi: tyres, compressors and pressure washers in the US and in many Pakistani workshops.
• bar: tyre pressure in Europe, scuba cylinders, boilers and hydraulics. 1 bar is close to 1 atmosphere.
• kPa and Pa: engineering, building ventilation, weather and scientific work.
• atm: chemistry and physics, where gases are compared to standard atmospheric pressure.
• mmHg and torr: medicine and vacuum technology. The two differ by less than 0.0001%, so they are treated as equal in practice.

Common mistakes to avoid

• Gauge vs absolute pressure. A tyre gauge reads gauge pressure (psig), relative to the atmosphere. Absolute pressure (psia) adds about 14.7 psi. Never mix them in gas-law calculations.
• Assuming 1 bar = 1 atm. They are close but not the same (1 atm = 1.01325 bar). The difference matters in precise work.
• Reading kPa as psi. A 220 kPa tyre is 32 psi. Inflating to "220 psi" would be dangerous.
• Safety-critical use. For pressure vessels, gas cylinders and medical devices, follow the manufacturer's or regulator's stated unit.

Exact conversion factors

Sources: BIPM, The International System of Units (SI Brochure); NIST Special Publication 811 (pressure units).

Frequently Asked Questions

How do I convert bar to psi?

Multiply bar by 14.5038. For example, 2.5 bar = 36.259 psi.

How do I convert psi to bar?

Multiply psi by 0.0689476. For example, 32 psi = 2.206 bar.

How many kPa is 1 psi?

1 psi is 6.894757 kPa (6,894.757 Pa).

What is standard atmospheric pressure?

1 atmosphere = 101,325 Pa = 101.325 kPa = 14.6959 psi = 760 mmHg.

What is 120 mmHg in kPa?

120 mmHg = 16 kPa.

Is bar the same as atmosphere?

No. 1 bar is 100,000 Pa and 1 atm is 101,325 Pa, so 1 atm is about 1.013 bar.

What is the difference between psig and psia?

psig is gauge pressure relative to the surrounding atmosphere, and psia is absolute pressure relative to a vacuum, about 14.7 psi higher at sea level.

All Pressure Conversions

Choose a starting unit to see every conversion available from it.

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