Pressure (symbolized by P) measures the perpendicular force exerted per unit of surface area (P = F / A). Across automotive engineering, HVAC refrigeration, hydraulics, aviation altimetry, meteorology, scuba diving, and vacuum physics, pressure measurement relies on two primary standards: the International System of Units (SI metric: Pascals, Kilopascals, Megapascals, Bar, Millibar) and US Customary / Industrial units (Pounds per Square Inch / PSI, Kip per Square Inch / KSI, Standard Atmospheres / atm, Torr / mmHg, Inches of Mercury / inHg, Feet of Water).
Our free online Pressure Converter provides instant, high-precision conversions across all metric, US customary, barometric, manometric, and ultra-high vacuum pressure units:
- Bar to PSI: Multiply bar by
14.5037738(1 bar = 100,000 Pa = 100 kPa = 14.50377 psi = 0.986923 atm). - PSI to Bar: Multiply psi by
0.06894757(1 psi = 6,894.757 Pa = 6.894757 kPa = 51.71493 mmHg). - Kilopascals to PSI: Multiply kPa by
0.14503774(100 kPa = 1 bar = 14.50377 psi). - Standard Atmospheres to Pascals:
1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.69595 psi = 760 mmHg. - Torr (mmHg at 0°C) to Pascals:
1 Torr = 133.322368 Pa = 1.333224 mbar = 0.019337 psi. - Inches of Mercury (inHg) to Millibar: Multiply inHg by
33.8638866(1 inHg = 33.86389 mbar = 25.4 mmHg = 3,386.389 Pa).
Master Pressure Unit Conversion Table
The table below displays exact physical relationships, SI power multipliers, and US Customary equivalents relative to 1 Pascal (Pa = 1 N/m²):
| Pressure Unit Name | Symbol | Exact Value in Pascals (Pa) | Equivalent in PSI & Bar | Domain & System Standard |
|---|---|---|---|---|
| 1 Pascal | Pa |
1.0 Pa (1 N/m²) |
0.000145038 psi (0.00001 bar) | SI Base Derived Unit (1 N/m²) |
| 1 Kilopascal | kPa |
1,000.0 Pa (103 Pa) | 0.145038 psi (0.01 bar) | SI Metric Tire & HVAC Unit |
| 1 Megapascal | MPa |
1,000,000.0 Pa (106 Pa) | 145.037738 psi (10.0 bar) | Structural Concrete & Hydraulic Systems |
| 1 Gigapascal | GPa |
1.0 × 109 Pa | 145,037.738 psi (10,000 bar) | Geophysics & Material Tensile Modulus |
| 1 Bar | bar |
100,000.0 Pa (100 kPa) |
14.503774 psi (0.986923 atm / 750.06 mmHg) |
European Automotive & Scuba Diving Standard |
| 1 Millibar | mbar, hPa |
100.0 Pa (1 hectopascal) | 0.014504 psi (0.001 bar) | Meteorology & Weather Barometric Unit |
| 1 Pound per Square Inch | psi, lbf/in² |
6,894.757293 Pa (6.894757 kPa) |
1.0 psi (0.068948 bar / 51.7149 mmHg) |
US Automotive, HVAC & Compressor Standard |
| 1 Kip per Square Inch | ksi |
6,894,757.29 Pa (6.894757 MPa) | 1,000.0 psi (68.94757 bar) |
US Civil Engineering Structural Steel Tensile Unit |
| 1 Standard Atmosphere | atm |
101,325.0 Pa (101.325 kPa) |
14.695949 psi (1.01325 bar / 760.0 mmHg) |
Sea-Level Mean Atmospheric Baseline (STP) |
| 1 Technical Atmosphere | at, kgf/cm² |
98,066.5 Pa (98.0665 kPa) | 14.223343 psi (0.980665 bar) | Historical Metric Gravitational Unit |
| 1 Torr (Millimeter Mercury 0°C) | Torr, mmHg |
133.322368 Pa (0.133322 kPa) |
0.019337 psi (0.001333 bar / 1/760 atm) | Clinical Blood Pressure & Vacuum Physics |
| 1 Inch of Mercury (32°F) | inHg |
3,386.38866 Pa (3.386389 kPa) | 0.491154 psi (33.86389 mbar / 25.4 mmHg) | US Aviation Altimeter Setting (QNH) |
| 1 Inch of Water (4°C) | inAq, inH‚O |
249.08891 Pa (2.490889 mbar) | 0.036127 psi (1.86832 mmHg) | HVAC Low Duct Static Differential Pressure |
| 1 Foot of Water (4°C) | ftAq, ftH‚O |
2,989.0669 Pa (29.89067 mbar) | 0.433527 psi (22.4198 mmHg) | Water Pump Total Dynamic Head (TDH) |
Step-by-Step Calculation Example
To convert an automobile tire pressure of 32 PSI (32 lbf/in²) into Bar, Kilopascals (kPa), and Standard Atmospheres (atm):
32 psi × 0.06894757 = 2.206322 Bar (2.21 bar)
32 psi × 6.894757 = 220.6322 Kilopascals (220.6 kPa)
32 psi ÷ 14.695949 = 2.17747 Standard Atmospheres (2.18 atm)
Thus, a 32 PSI tire recommendation equals 2.21 bar, 220.6 kPa, or 2.18 atm.
Real-World Mechanical & Atmospheric Pressure Benchmarks
Below is a comparative reference chart showing pressures across ultra-high vacuums, blood pressure, tires, scuba tanks, ocean trenches, and planetary cores:
| Environment / Application | Pressure in Metric Units (Pa / kPa / bar) | Pressure in Imperial / Manometric (psi / mmHg) | Mechanical & Physical Context |
|---|---|---|---|
| Ultra-High Vacuum (UHV Chamber) | 1.0 × 10-7 Pa (10-9 mbar) | 7.5 × 10-10 Torr (1.45 × 10-11 psi) | Particle accelerator beam pipe vacuum level |
| Normal Human Systolic Blood Pressure | 16.0 kPa (160 mbar) | 120.0 mmHg (2.32 psi) | Standard clinical arterial systolic blood pressure mean |
| Sea-Level Standard Atmospheric Baseline | 101.325 kPa (1.01325 bar) | 14.696 psi (760.0 mmHg / 29.92 inHg) | Standard 1.0 atm international reference pressure |
| Automobile Passenger Tire Inflation | 220.0 to 240.0 kPa (2.2 to 2.4 bar) | 32.0 to 35.0 psi | Standard cold pneumatic tire pressure gauge reading |
| Filled Scuba Diving Cylinder Tank | 20.0 MPa (200.0 bar) | 2,900.0 psi (197.4 atm) | Standard compressed breathing gas scuba tank capacity |
| Mariana Trench Ocean Floor Depth (10,994m) | 108.6 MPa (1,086.0 bar) | 15,750.0 psi (1,071.8 atm) | Deepest abyssal ocean hydrostatic water column pressure |
| Planet Earth Inner Core Boundary | 360.0 GPa (3.6 × 106 bar) | 52.21 × 106 psi (3.55 × 106 atm) | Gravitational compression at Earth’s solid iron core |
History & Standards: Evangelista Torricelli vs. Blaise Pascal vs. Vilhelm Bjerknes
Evangelista Torricelli and the Mercury Barometer (1643)
In 1643, Italian mathematician and physicist Evangelista Torricelli (a student of Galileo Galilei) inverted a glass tube filled with mercury into a basin of mercury, inventing the first atmospheric barometer. He demonstrated that atmospheric air weight supports a column of mercury approximately 760 mm high at sea level. The unit Torr (1 Torr = 1 mmHg = 133.322 Pa) was named in his honor.
Blaise Pascal and Altitude Pressure (1648 / 1971)
In September 1648, French philosopher and mathematician Blaise Pascal instructed his brother-in-law Florin Périer to carry a mercury barometer up the Puy de Dôme mountain, proving empirically that atmospheric pressure decreases with altitude. In 1971, the 14th General Conference on Weights and Measures (CGPM) adopted the Pascal (Pa) as the official SI unit for pressure, defined as 1 Newton per square meter (1 Pa = 1 N/m²).
Vilhelm Bjerknes and the Bar (1909)
In 1909, Norwegian meteorologist Vilhelm Bjerknes (founder of modern weather forecasting) introduced the bar (from Greek baros, meaning weight) defined as exactly 100,000 Pascals (105 N/m²). Because 1 bar is virtually identical to 1 atmosphere (1 atm = 1.01325 bar), meteorologists adopted the millibar (mbar) and hectopascal (hPa) worldwide for isobaric weather charts.
Popular direct conversions:
- Bar to PSI Converter | PSI to Bar Converter
- KPa to PSI Converter | PSI to KPa Converter
- Conversion Calculator Main Directory
Frequently Asked Questions (FAQ)
How many PSI are in 1 Bar?
There are approximately 14.503774 PSI in 1 Bar (or 1 bar = 100 kPa).
How many Kilopascals (kPa) are in 1 PSI?
There are approximately 6.894757 kPa in 1 PSI (1 psi = 6,894.757 Pascals).
What is standard atmospheric pressure at sea level?
Standard atmospheric pressure (1 atm) equals exactly 101,325 Pascals (101.325 kPa), 1.01325 bar, 14.69595 PSI, 760 mmHg (Torr), or 29.921 inHg.
Why is automobile tire pressure measured in PSI or Bar?
In the US, tire pressure is measured in PSI (pounds per square inch), where 32 to 35 PSI is typical. In Europe and metric regions, tire pressure is measured in Bar (2.2 to 2.4 bar) or Kilopascals (kPa) (220 to 240 kPa).