Pounds per square inch

A pressure gauge reading in psi (red scale) and kPa (black scale)

The pound per square inch or, more accurately, pound-force per square inch (symbol: psi or lbf/in² or lb_f/in² or lbf/sq in or lb_f/sq in) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to an area of one square inch:

One pound per square inch approximately equals 6,894.757 Pa.

Magnitude

Main article: Orders of magnitude (pressure)

• Blood Pressure – Average human blood pressure (120/80): 2.32psi/1.55psi
• Boost Pressure Provided By an Automotive Turbocharger(common):P_g = 6–15psi
• Atmospheric pressure at sea level (standard): P_a = 14.7 psi
• Automobile tire overpressure (common): P_g = 32 psi
• Bicycle tire overpressure (common): P_g = 65 psi
• Workshop or garage air tools: P_g = 90 psi
• Air brake (rail) or Air brake (road vehicle) reservoir overpressure (common): 90 psi ≤ P_g ≤ 120 psi
• Road racing bicycle tire overpressure: P_g = 120 psi
• Steam locomotive fire tube boiler (UK, 20th century): 150 psi ≤ P_g ≤ 280 psi
• Union Pacific Big Boy steam locomotive boiler: 300 psi
• Natural gas pipelines: 800 to 1000 psi
• Full SCBA Self Contained Breathing Apparatus for toxic atmospheres: 2216 psi
• Full scuba tank overpressure (common): P_g = 3000 psi
• Commercial jet airliner hydraulic pressure: 3000 psi
• Airbus A380 hydraulic system: 5000 psi
• Water jet cutter: 40,000–100,000 psi
• Young's Modulus for steel: 30 Mpsi or 30,000,000 psi

Conversions

Pressure units

	pascal	bar	technical atmosphere	standard atmosphere	torr	pound per square inch
	Pa	bar	at	atm	Torr	psi
1 Pa	≡ 1 N/m2	10−5	1.0197×10−5	9.8692×10−6	7.5006×10−3	145.04×10−6
1 bar	105	≡ 106 dyn/cm2	1.0197	0.98692	750.06	14.5037744
1 at	0.980665 ×105	0.980665	≡ 1 kp/cm2	0.96784	735.56	14.223
1 atm	1.01325 ×105	1.01325	1.0332	≡ p0	760	14.696
1 Torr	133.322	1.3332×10−3	1.3595×10−3	1.3158×10−3	= 1 mmHg	19.337×10−3
1 psi	6.895×103	68.948×10−3	70.307×10−3	68.046×10−3	51.715	≡ 1 lbF/in2

See also

• Conversion of units: Pressure or mechanical stress
• Pressure: Units

External links

• Pressure measurement primer
• Online pressure conversions