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Convert between all major pressure units instantly. Supports PSI, bar, atm, kPa, Pa, MPa, mbar, mmHg, torr, and inHg with real-time calculations and quick-select presets.
This table shows how 1 unit of each pressure measurement converts to all other units. Use it as a quick reference when working with different pressure scales in engineering, medical, or scientific contexts.
| Unit | Pa | kPa | bar | PSI | atm | mmHg | inHg |
|---|---|---|---|---|---|---|---|
| 1 Pa | 1 | 0.001 | 0.00001 | 0.000145 | 9.87 × 10⁻&sup6; | 0.00750 | 0.000295 |
| 1 kPa | 1,000 | 1 | 0.01 | 0.14504 | 0.00987 | 7.5006 | 0.2953 |
| 1 bar | 100,000 | 100 | 1 | 14.5038 | 0.98692 | 750.06 | 29.530 |
| 1 PSI | 6,894.76 | 6.8948 | 0.06895 | 1 | 0.06805 | 51.715 | 2.0360 |
| 1 atm | 101,325 | 101.325 | 1.01325 | 14.696 | 1 | 760.00 | 29.921 |
| 1 mmHg | 133.322 | 0.13332 | 0.00133 | 0.01934 | 0.00132 | 1 | 0.03937 |
| 1 inHg | 3,386.39 | 3.3864 | 0.03386 | 0.49115 | 0.03342 | 25.400 | 1 |
| 1 MPa | 1,000,000 | 1,000 | 10 | 145.038 | 9.8692 | 7,500.6 | 295.30 |
| 1 mbar | 100 | 0.1 | 0.001 | 0.01450 | 0.000987 | 0.75006 | 0.02953 |
Pressure is the force applied perpendicular to a surface per unit area. In physics, it is expressed as P = F / A, where F is force in newtons and A is area in square meters. The SI unit of pressure is the pascal (Pa), defined as one newton per square meter. Because a single pascal represents a very small amount of pressure, practical measurements typically use kilopascals (kPa), megapascals (MPa), or the non-SI unit bar (1 bar = 100,000 Pa).
Different industries have adopted various pressure units over time. PSI (pounds per square inch) is the standard in North American automotive and industrial sectors. Bar is widely used in European engineering and compressed gas applications. Atmosphere (atm) serves as a reference in chemistry and diving, defined as the average air pressure at sea level. Millimeters of mercury (mmHg), also called torr, remains the universal standard for blood pressure in medicine, originating from early mercury-column manometers. Inches of mercury (inHg) is used in US weather reporting and aviation altimeter settings. Millibar (mbar), equivalent to the hectopascal (hPa), is the preferred unit in meteorology worldwide.
Understanding how to convert between these units is essential for professionals working across international borders, interpreting equipment specifications, reading scientific literature, and ensuring safety in pressurized systems from hydraulic lines to medical devices.
The simplest approach is to convert any pressure value to pascals first (the base SI unit), then convert from pascals to the target unit. Multiply the input by its “to pascals” factor, then divide by the target unit’s factor.
Result = Value × (Source Factor ÷ Target Factor)
Where each factor is the number of pascals in one unit of that type
Context: 32 PSI is a typical car tire inflation pressure, which equals about 2.21 bar.
Context: 120 mmHg is the systolic value of normal blood pressure (120/80 mmHg).
Context: 3 atm is the pressure at approximately 20 meters depth in seawater (2 atm water + 1 atm air).
For a quick PSI-to-bar approximation, divide PSI by 14.5 (or multiply by 0.069). For bar-to-PSI, multiply bar by 14.5. For atm-to-PSI, multiply by 14.7. These rough conversions are accurate to within about 1% and are useful for quick field estimates.
Real-world pressure values span an enormous range, from the near-vacuum of outer space to the extreme pressures inside industrial hydraulic systems. This table shows commonly encountered pressure values across different fields.
| Application | PSI | bar | kPa | atm |
|---|---|---|---|---|
| Bicycle tire (road) | 100 | 6.89 | 689.5 | 6.80 |
| Car tire (typical) | 32 | 2.21 | 220.6 | 2.18 |
| Truck tire | 80 | 5.52 | 551.6 | 5.44 |
| Football (soccer ball) | 12 | 0.83 | 82.7 | 0.82 |
| Household water supply | 50 | 3.45 | 344.7 | 3.40 |
| Application | mmHg | kPa | PSI | atm |
|---|---|---|---|---|
| Normal blood pressure (systolic) | 120 | 16.0 | 2.32 | 0.158 |
| Normal blood pressure (diastolic) | 80 | 10.7 | 1.55 | 0.105 |
| High blood pressure (stage 2) | 140 | 18.7 | 2.71 | 0.184 |
| Sea level atmosphere | 760 | 101.3 | 14.70 | 1.000 |
| Airplane cabin (cruising) | 570 | 75.9 | 11.02 | 0.750 |
| Application | PSI | bar | MPa | atm |
|---|---|---|---|---|
| Scuba tank (full) | 3,000 | 207 | 20.7 | 204 |
| Depth at 30 m seawater | 58.8 | 4.05 | 0.405 | 4.0 |
| Hydraulic press | 5,000 | 345 | 34.5 | 340 |
| Pressure washer | 2,000 | 138 | 13.8 | 136 |
| Water jet cutting | 60,000 | 4,137 | 413.7 | 4,082 |
Engineers work with specifications from international suppliers that use bar, PSI, or kPa. Misinterpreting a pressure rating can lead to equipment failure, safety hazards, or costly recalls. Accurate conversion ensures hydraulic systems, boilers, and pneumatic tools operate within safe limits.
Blood pressure is universally recorded in mmHg, while ventilator settings may use cmH2O or mbar. Medical professionals interpreting international research or calibrating equipment must convert accurately. Errors in pressure readings can affect diagnoses and treatment decisions.
Meteorologists use mbar or hPa internationally, while US weather reports use inHg. Pilots must set altimeter pressure in inHg (US) or hPa (ICAO standard). Correct conversion is critical for flight safety, storm tracking, and barometric pressure interpretation.
Tire pressure is specified in PSI in North America, kPa in Asia-Pacific markets, and bar in Europe. Vehicle owners traveling internationally, importing cars, or reading foreign tire specifications need reliable conversions to maintain proper inflation and safe driving conditions.
A tire at 32 PSI gauge (PSIG) is actually at 46.7 PSI absolute (PSIA). When converting between units, make sure you know whether your source value is gauge or absolute. Most everyday measurements (tires, compressors) are gauge pressure, while scientific calculations typically use absolute pressure.
The jump between Pa, kPa, and MPa involves factors of 1,000. Confusing kPa with Pa (or MPa with kPa) creates errors of three orders of magnitude. Double-check your prefix when reading specifications: 250 kPa is vastly different from 250 Pa.
One millibar equals one hectopascal (1 mbar = 1 hPa = 100 Pa). Weather services use these interchangeably. If you see a barometric reading of 1013.25 hPa, it is the same as 1013.25 mbar. No conversion is needed between these two units.
Pressure conversions often produce long decimal values. Match your precision to the application: tire pressure to 1 decimal place is sufficient, while scientific work may require 4 or more significant figures. Rounding too aggressively can introduce meaningful errors in precision applications.
Pressure gauges, compressors, and regulators may display in different units depending on the manufacturer and market. Always check the unit label on the gauge dial or display before assuming PSI or bar. Using a gauge reading in the wrong unit can lead to dangerous over- or under-pressurization.
Gauge pressure measures pressure relative to atmospheric pressure, where zero represents atmospheric pressure. Absolute pressure includes atmospheric pressure in the measurement, where zero represents a perfect vacuum. For example, a tire at 32 PSIG (gauge) is at about 46.7 PSIA (absolute) when accounting for the 14.696 PSI of atmospheric pressure at sea level.
To convert PSI to bar, multiply the PSI value by 0.0689476. For example, 100 PSI equals 100 multiplied by 0.0689476, which gives 6.89476 bar. Conversely, to convert bar to PSI, multiply the bar value by 14.5038.
Torr is named after Evangelista Torricelli, inventor of the barometer. Originally, 1 torr was defined as 1/760 of a standard atmosphere, while 1 mmHg was based on the height of a mercury column. Modern definitions make them virtually identical, differing by less than 0.000015 percent, so they are used interchangeably in practice.
Standard atmospheric pressure at sea level is defined as exactly 101,325 Pa (pascals), which equals 1 atm, 1.01325 bar, 1013.25 mbar (hPa), 14.696 PSI, 760 mmHg, 760 torr, and 29.9213 inHg. These values serve as reference points for calibrating instruments and defining measurement standards.
Scuba diving uses bar for tank pressure (typically 200 to 300 bar) and atmospheres for depth-related pressure. Each 10 meters of seawater depth adds approximately 1 atmosphere of pressure. At 30 meters depth, a diver experiences about 4 atm total: 1 atm from the air above plus 3 atm from the water column. In the US, divers may also reference tank pressure in PSI (3,000 to 4,500 PSI).
Blood pressure is measured in millimeters of mercury because early sphygmomanometers used a column of mercury to measure arterial pressure. Although modern digital devices use electronic sensors, the mmHg unit persists as the worldwide medical standard for consistency in clinical records, research, and international communication. Normal blood pressure is around 120/80 mmHg.
Choose based on your industry and region. Use PSI for North American automotive and industrial work, bar for European engineering, kPa for international tire pressure standards, mmHg for medical applications such as blood pressure, atm for chemistry and diving depth calculations, and pascals or kilopascals for scientific research. Always check equipment specifications and industry standards for your specific field.
One bar equals exactly 100,000 pascals (100 kPa or 0.1 MPa). The bar was introduced as a convenient unit because atmospheric pressure is approximately 1 bar (1.01325 bar to be exact). While not an official SI unit, bar is widely accepted in engineering, meteorology, and industrial applications due to its practical scale for everyday pressures.
This pressure converter is provided for educational and reference purposes only. While we strive for accuracy, always verify critical pressure values with calibrated instruments and consult professional engineers for safety-critical applications. UnitTables is not liable for any errors or damages resulting from the use of this tool.