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Pressure Unit Conversion Chart

Quick reference guide for pressure measurement units

Standard Pressure Units

Unit	Symbol	SI Equivalent	Description
Pascal	Pa	N/m²	SI unit of pressure
Kilopascal	kPa	1,000 Pa	Common metric unit
Megapascal	MPa	1,000,000 Pa	Industrial/engineering applications
Bar	bar	100,000 Pa	Metric unit close to 1 atmosphere
Pound per square inch	psi	6,894.76 Pa	Imperial/US customary unit
Atmosphere	atm	101,325 Pa	Standard atmospheric pressure
Torr/millimeter of mercury	Torr/mmHg	133.322 Pa	Medical/vacuum measurements

Specialized Pressure Units

Unit	Symbol	SI Equivalent	Application
Inch of water column	inH₂O	249.089 Pa	HVAC, low-pressure applications
Inch of mercury	inHg	3,386.39 Pa	Weather forecasting, vacuum measurement
Kilogram-force per square centimeter	kgf/cm²	98,066.5 Pa	Industrial applications
Hectopascal	hPa	100 Pa	Meteorology
Millibar	mbar	100 Pa	Weather forecasting
Kilopound per square inch	ksi	6,894,760 Pa	Materials engineering, structural analysis

Pressure per Length Units

Unit	Symbol	SI Equivalent	Application
Pascal per meter	Pa/m	Pa/m	Pressure gradients, fluid dynamics
Pound per square inch per foot	psi/ft	22,620.6 Pa/m	Oil/gas well engineering
Bar per kilometer	bar/km	100 Pa/m	Pipeline pressure gradients
Millimeter of water column per meter	mmH₂O/m	9.80665 Pa/m	Hydronic systems, HVAC

Common Pressure Unit Conversions

From	To	Conversion Factor	Example
Bar	PSI	Multiply by 14.5038	1 bar = 14.5038 psi
PSI	Bar	Multiply by 0.0689476	1 psi = 0.0689476 bar
kPa	PSI	Multiply by 0.145038	100 kPa = 14.5038 psi
Atmosphere	Bar	Multiply by 1.01325	1 atm = 1.01325 bar
mmHg	kPa	Multiply by 0.133322	760 mmHg = 101.325 kPa
inH₂O	PSI	Multiply by 0.036127	27.71 inH₂O = 1 psi
MPa	Bar	Multiply by 10	1 MPa = 10 bar
inHg	Bar	Multiply by 0.0338639	29.92 inHg = 1.01325 bar

Reference Values for Pressure

Pressure Level	kPa	Bar	PSI	Notes
Standard atmospheric pressure	101.325	1.01325	14.6959	At sea level
Car tire pressure (typical)	220 - 250	2.2 - 2.5	32 - 36	Passenger vehicles
Bicycle tire pressure (road)	550 - 830	5.5 - 8.3	80 - 120	Depends on tire type
Home water supply	275 - 520	2.75 - 5.2	40 - 75	Residential plumbing
Normal blood pressure (systolic)	16	0.16	2.32	120 mmHg
Steam boiler (medium pressure)	1000 - 2000	10 - 20	145 - 290	Industrial applications
Hydraulic systems (typical)	10,000 - 35,000	100 - 350	1,450 - 5,075	Industrial equipment
SCUBA tank (filled)	20,700	207	3,000	Standard aluminum tank

Key Pressure Equations

Hydrostatic pressure: P = ρgh (P = pressure, ρ = density, g = gravitational acceleration, h = height of fluid column)
Ideal gas law: P = nRT/V (P = pressure, n = moles of gas, R = gas constant, T = temperature, V = volume)
Gauge vs. absolute pressure: P_absolute = P_gauge + P_atmospheric
Pressure vs. force: P = F/A (P = pressure, F = force, A = area)
Pressure conversion formula: P_new = P_old × (conversion factor)
Pressure drop in pipe: ΔP = f × (L/D) × (ρv²/2) (f = friction factor, L = length, D = diameter, ρ = density, v = velocity)
Depth to pressure conversion (water): P (bar) = 0.0980665 × depth (meters) + 1.01325

Practical Examples of Pressure Conversions

Tire Pressure

When filling car tires, pressure gauges might read in PSI, bar, or kPa. A recommended tire pressure of 35 PSI equals 2.41 bar or 241 kPa. In European countries, pressure is typically specified in bar, while North American vehicles typically specify PSI.

Weather Forecasting

Meteorologists use millibars (mb) or hectopascals (hPa) to report atmospheric pressure. A typical high-pressure system might read 1030 hPa (30.42 inHg), while a low-pressure system might be around 990 hPa (29.23 inHg). Barometric pressure relates to weather patterns.

Medical Applications

Blood pressure is typically measured in millimeters of mercury (mmHg). A normal reading of 120/80 mmHg corresponds to 16.0/10.7 kPa. Medical vacuum systems often operate at -300 mmHg to -600 mmHg (relative to atmospheric pressure), which is -40 to -80 kPa.

Industrial Hydraulics

Industrial hydraulic systems typically operate at pressures from 2,000 to 5,000 PSI (138 to 345 bar). A hydraulic press generating 4,000 PSI (276 bar) on a 5-square inch piston would produce 20,000 pounds of force, demonstrating the pressure-force relationship.