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psi – Pounds per Square Inch Pressure Unit

Pounds or pound force per square inch (psi, lb/in², pfsi or lbf/in²) is a widely used British and American unit of measure for pressure. 1 psi equals 6,894.76 pascals.

In the USA the PSI pressure unit is the primary unit of measure for pressure and almost all pressure instruments are specified and display in pounds per square inch.

The psi is still used extensively in the UK but the bar pressure unit has mostly replaced it as the primary pressure unit.

Use the conversion factors below to convert from PSI to other pressure units or vice versa. To convert a reading in PSI to another unit multiply it by the relevant pressure conversion factor. To convert a reading in any pressure unit to PSI divide it by the relevant pressure conversion factor. Alternatively convert from a psi pressure value into another unit using the psi conversion table or the pressure unit converter.

Find out how psi is derived from SI units and view the alternative descriptions for psi.

Conversion Factors

Please note that the conversion factors above are accurate to 6 significant figures.

Derivation

The calculation below shows how the pressure unit pounds per Square inch (psi) is derived from SI Units.

Formula

  • Pressure = Force / Area
  • Force = Mass x Acceleration
  • Acceleration = Distance / (Time x Time)

SI Units

  • Mass: kilogram (kg)
  • Length: metre (m)
  • Time: second (s)
  • Force: newton (N)
  • Pressure: pascal (Pa)

Input Values

  • 1 Pound = 0.45359237 kg
  • 1 Inch = 0.0254 m
  • 1 Square Inch = 0.0254 m x 0.0254 m = 0.00064516 m²
  • Acceleration = Standard Gravity = 9.80665 m/s²

Calculation

  • 1 Pound Force = 0.45359237 kg x 9.80665 m/s² = 4.448221615 N
  • 1 psi Pressure = 4.448221615 N / 0.00064516 m² = 6894.757293 Pa

Alternate Descriptions

These are the different versions used for identifying psi that you may find elsewhere.

  • Pounds Per Square Inch
  • Pound Per Square Inch
  • Pounds Force Per Square Inch
  • Pound Force Per Square Inch
  • psi
  • pfsi
  • lb/in²
  • lbf/in²
  • lb/sq in
  • lbf/sq in
  • lb/in^2
  • lbf/in^2
  • lbs/in²
  • lbsf/in²
  • lbs/sq in
  • lbsf/sq in
  • lbs/in^2
  • lbsf/in^2

Conversion Tables

Select a look up table for converting a pressure reading in pounds per square inch to other measurement units.

  • mbar, hPa, Bar, inHg, mH2O, inH2O and ftH2O
  • bar  »  1 to 100,000 psi → 0.0689476 to 6,894.76 bar
  • mbar  »  0.1 psi to 100.0 psi → 6.89476 to 6,894.76 mbar
  • Pa  »  0.01 psi to 20.00 psi → 68.9476 to 137,895 Pa
  • hPa  »  0.1 psi to 100.0 psi → 6.89476 to 6,894.76 hPa
  • kPa  »  1 to 1,000 psi → 6.89476 to 6,894.76 kPa
  • MPa  »  100 to 100,000 psi → 0.689476 to 689.476 MPa
  • kg/cm²  »  1 to 100,000 psi  → 0.0703070 to 7,030.70 kg/cm²
  • mH2O  »  1 to 1000 psi → 0.703070 to 703.070 mH2O
  • inH2O  »  0.01 to 20.01 psi → 0.276799 to 553.598 inH2O
  • ftH2O  »  1 to 1,000 psi → 2.30666 to 2,306.66 ftH2O
  • mmHg  »  0.01 to 20.00 psi → 0.517149 to 1,034.30 mmHg
  • inHg  »  0.01 to 20.00 psi → 0.0203602 to 40.7204 mmHg

Help

20,000 psi to bar

What would be bar conversion scale for 0-20,000 psi range?

20,000 psi = 1,378.95… bar

0-40000psi to bar scale

780 psi to kPa

How to convert 780 psi to kPa?

780 psi = 5377.91 kPa

0-1560psi to kPa Conversion Scale

1 psi to oz/in²

How many oz/in² are there in 1 psi?

There are 16 oz in 1 lb, so 1 psi = 16 oz/in²

The 0-2 psi conversion scale below shows the conversion values around 1 psi.

0-2psi to ozin conversion scale

0-200 psi to bar

What is european bar equivalent values for a 0-200 psi range?

This graphic shows the equivalent bar values over the range 0 to 200 psi:

0 to 200 psi to bar Conversion Scale

lbf/in² meaning

What is  meaning of lbf/in² and the relationship to bar?

“lbf/in²” is one of the many acronyms used for “Pounds Force per Square Inch” pressure units of which “psi” is the most commonly used.  The factor for converting lbf/in² into bar is 0.068948., e.g. 15 psi = 1.03422 bar.

psi to bar

What is the equation for psi to bar?

psi to bar = multiply by 0.0689476…

psi to bar

What is the equation for psi to kPa?

psi to kPa = multiply by 6.89476…

22.2 psi to ftH2O

How do I convert 22.2 psi to feet of water and what is it?

1 psi = 2.30666 feet of water, therefore 22.2 psi = 51.2 feet of water.

The pressure unit “Feet of Water” is the pressure that a 1 foot high column of water exerts under the influence of gravity.

e.g. A storage tank which contains water up to a level of 51.2 feet will push down on the bottom of the tank with a pressure of 22.2 psi.

Seawater depth into psi

What is the reading in psi at 5000 ft below the surface of the ocean?

It’s approximately 2,168 psi if you assume the specific gravity density of freshwater at 4 degC of 1.0, the actual pressure will vary by a few percent depending the seawater properties.  Seawater has a varying density due to variations in salinity, temperature and pressure at different depths and geo-locations.

USA and UK psi

Is the US measure of psi the same as the UK?

Yes a USA psi is the same amount as a UK psi.

Measurement Unit Related Terms

More pages related to measurement unit technical terms.