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Pressure Converter - Bar, psi, pascal, atmospheres

Convert pressure units like bar, psi, pascals (Pa), and atmospheres (atm) instantly and locally.

Pressure Reference Table

Unit Pascal (Pa) Bar psi atm
1 Pa 1 0.00001 0.000145 9.86923e-6
1 kPa 1000 0.01 0.145038 0.009869
1 bar 100 000 1 14.50377 0.986923
1 psi 6894.757 0.068948 1 0.068046
1 atm 101 325 1.01325 14.69595 1

How pressure conversion is calculated

Pressure is defined as force per unit area. The official SI unit of pressure is the pascal (Pa), which is equal to one newton per square meter (N/m²). Since one pascal is a very small amount of pressure, kilopascals (kPa) or bar are more commonly used in practice. Psi is widely used in the US and for tire pressure, while atm measures standard atmospheric pressure.

  • 1 kilopascal (kPa) = 1,000 pascals (Pa)
  • 1 bar = exactly 100,000 pascals (Pa) ≈ 14.5038 psi
  • 1 psi (pound per square inch) = exactly 6,894.757293168 pascals (Pa)
  • 1 standard atmosphere (atm) = exactly 101,325 pascals (Pa) = 1.01325 bar

About this tool

The pressure converter turns pascal (Pa), kilopascal (kPa), bar, psi, mmHg, atmospheres and torr into each other. Useful for tire pressure, weather forecasts, blood pressure, hydraulics, vacuum systems, diving and HVAC. The standard atmosphere (1 atm) at sea level is 101,325 Pa = 1013.25 hPa = 1.01325 bar = 14.696 psi = 760 mmHg. All computed locally in the browser, no server calls.

How to use it

  1. Pick the unit you’re starting from (e.g. bar).
  2. Type the numeric value.
  3. All other units update automatically.
  4. Copy or read off the value you need.

Examples

Car tire pressure
Input32 psi
Output2.207 bar = 220.6 kPa = 220 632 Pa
Blood pressure 120/80
Input120 mmHg (systolic)
Output16.0 kPa = 0.158 atm
Blood pressure is historically measured in mmHg because early manometers used a mercury column. Medicine keeps mmHg even though SI would prefer kPa.

Common use cases

  • Car and bike tires (bar/psi) and compressed air.
  • Weather forecast (hPa/mbar) and pressure changes.
  • Blood pressure and medical devices (mmHg).
  • Diving (bar/atm), where 10 m depth adds 1 bar.
  • Hydraulics and pneumatics (MPa, bar).

Frequently asked questions

Bar vs pascal, what’s the difference?
Pascal is the SI unit (1 Pa = 1 N/m²), but it’s tiny. 1 bar = 100,000 Pa = 100 kPa (exact by definition). Bar is convenient because it’s close to 1 atm and gives "manageable" everyday numbers, while Pa is used in science and formulas. hPa (hectopascal) in weather = mbar historically, since both equal 100 Pa.
Absolute vs gauge pressure?
Absolute pressure is measured from perfect vacuum (0 = nothing). Gauge (relative) pressure is measured from atmospheric. A tire gauge showing "2.2 bar" is gauge, absolute pressure is 2.2 + 1.013 = 3.213 bar. In English units this is psi vs psia (absolute) vs psig (gauge). Vacuum work typically uses absolute (Pa/torr). Always check which reference your number uses.
Why do weather reports use hPa?
Meteorologists historically used millibar (mbar). When SI came in, they wanted to keep the same numbers, and since 1 mbar = 100 Pa = 1 hPa, hPa was the perfect drop-in. Normal air pressure is 1013 hPa/mbar, high pressure over 1020, low pressure under 1000. The equivalent in kPa (101.3 kPa) is technically fine but less handy because 1 hPa steps are meaningful in weather analysis.
Are 1 atm and 1 bar the same?
Almost. 1 atm = 101,325 Pa (exact, defined in 1954), 1 bar = 100,000 Pa (exact). The difference is 1.325%, noticeable in precision work but negligible day to day. Standard tables for gas, boiling points etc. usually use "STP" or "NTP" defined via atm (or the newer IUPAC definition with 100 kPa = 1 bar). In diving, 1 atm ≈ 1 bar is used for simplicity.

Technical background

The SI unit is pascal, Pa = N/m² = kg/(m·s²). Conversion constants (all exact unless noted): 1 kPa = 1000 Pa, 1 MPa = 10⁶ Pa, 1 bar = 100,000 Pa, 1 mbar = 1 hPa = 100 Pa, 1 atm = 101,325 Pa, 1 psi = 6894.757 Pa (from 1 lbf/in² with lbf exactly defined), 1 mmHg = 133.322387415 Pa (depends on mercury density and gravity; standard at 0°C and g = 9.80665 m/s²), 1 torr = 101,325/760 Pa ≈ 133.3224 Pa (nearly but not exactly equal to mmHg), 1 inHg = 25.4 mm × 133.322... ≈ 3386.389 Pa. Standard atmosphere decreases with altitude: the barometric formula gives ~12 hPa/100 m at low altitude. The calculator uses double-precision IEEE 754, giving 15–17 significant figures, ample for all practical pressure conversions. Everything runs in the browser, no data leaves the device.