Pressure Converter Online - Professional Pressure Unit Calculator
Our free online pressure converter is the most accurate tool for converting pressure units between different measurement systems. The calculator supports over 25 formats, including metric (SI), imperial, atmospheric, and special pressure measurement systems.
Most Popular Pressure Conversions
PSI to bar (PSI → bar): the most common pressure conversion between American and metric systems. To convert, divide by 14.5038. For example, 100 PSI = 6.89 bar. Used in automotive industry for tire pressure, hydraulic systems, pneumatic equipment. PSI is standard in the US and Canada, while bar dominates in Europe and most international applications.
Bar to PSI (bar → PSI): reverse conversion from metric to American system. To convert, multiply by 14.5038. For example, 1 bar = 14.5 PSI. Critical for importing/exporting equipment, international projects, working with US standards and technical requirements when dealing with European or international equipment specifications.
Atmospheres to pascals (atm → Pa): conversion between traditional atmospheric unit and SI base unit. To convert, multiply by 101325. For example, 1 atm = 101325 Pa = 101.325 kPa. Atmosphere is defined as standard atmospheric pressure at sea level at 32°F (0°C) and is used in scientific calculations, meteorology, and as reference value.
Millimeters of mercury to torr (mmHg → Torr): practically identical conversion since these units are nearly equal. 1 mmHg ≈ 1 Torr (difference less than 0.000015%). Used in medicine for blood pressure measurement, laboratory vacuum systems, barometric measurements. Torr is named after Evangelista Torricelli, inventor of the barometer.
Kilopascals to bar (kPa → bar): conversion between SI units and technical unit. To convert, divide by 100. For example, 250 kPa = 2.5 bar. Kilopascal is widely used in engineering calculations, technical documentation, building codes, while bar is more convenient for practical measurements and industrial equipment.
Pressure Measurement Systems
International System of Units (SI): based on pascal (Pa) as the fundamental pressure unit, equal to one newton per square meter (N/m²). Includes multiples: kilopascal (kPa = 1000 Pa), megapascal (MPa = 1,000,000 Pa), hectopascal (hPa = 100 Pa). Pascal is very small for practical use, so kilopascals and megapascals are more commonly applied. SI system is mandatory in scientific literature and international standards.
Technical System: based on bar as the main unit. Bar equals 100,000 Pa and approximately corresponds to atmospheric pressure (1 bar ≈ 0.987 atm). Includes millibar (mbar = 0.001 bar), widely used in meteorology. PSI (pounds per square inch) is the main unit in the Anglo-American system, popular in US, Canada, and UK. Technical systems are convenient for industrial applications due to practical numerical values.
Atmospheric System: based on atmospheric pressure as reference. Standard atmosphere (atm) is defined as 101325 Pa and corresponds to standard atmospheric pressure at sea level. Technical atmosphere (at) equals 98066.5 Pa and corresponds to pressure of 10-meter water column. Millimeters of mercury (mmHg) and torr are used for high-precision measurements, especially in vacuum technologies.
Manometric Units: based on liquid column height under gravity. Millimeters and inches of mercury (mmHg, inHg) are used in barometers and medical equipment. Water column (mmH₂O, inH₂O) is applied for measuring small pressures, for example, in ventilation systems. These units depend on liquid density and gravitational acceleration.
Practical Applications of Pressure Converter
Automotive Industry: converting tire pressure between different standards. European manufacturers use bar, American ones use PSI. Correct pressure is critical for safety, fuel economy, tire wear. Also important for hydraulic systems, pneumatic truck brakes, suspension systems. Conversion errors can lead to accidents, premature equipment wear, warranty violations.
Industrial Equipment: setting up and calibrating pressure in various systems. Hydraulic presses operate at pressures of 200-700 bar (2900-10150 PSI), pneumatic systems at 6-10 bar (87-145 PSI). Compressors, pumps, valves have specifications in different units depending on manufacturer. Conversion is necessary for selecting compatible equipment, calculating operating parameters, ensuring operational safety.
Medicine and Healthcare: blood pressure measurement is traditionally done in millimeters of mercury (mmHg). Normal pressure 120/80 mmHg corresponds to 16.0/10.7 kPa or 2.32/1.16 PSI. Respirators, anesthesia machines, dialysis equipment use different pressure units. Conversion is critically important for patient safety, medical equipment setup, international medical documentation.
Scientific Research: experiments often require precise pressure control in specific units. Vacuum technologies use torr or millibars for high vacuum (10⁻⁹ - 10⁻³ torr). Chemical reactions under pressure require accurate conversion between atmospheres, bars, and pascals. Materials science studies properties under extreme pressures up to gigapascals (GPa).
Aviation and Aerospace: barometric altimeters use inches of mercury or millibars to measure atmospheric pressure at different altitudes. Aircraft cabins maintain pressure equivalent to 8000 feet (about 0.75 atm). Space suits operate at 0.3 atm pure oxygen pressure. Conversion between different systems is critical for flight safety, international avionics compatibility.
Oil and Gas Industry: wells operate at pressures from several bars to hundreds of megapascals. Gas transportation occurs at pressures of 40-100 bar (580-1450 PSI). Refineries use different pressure units depending on process: PSI for American equipment, bars for European, atmospheres for calculations. Conversion errors can lead to accidents, explosions, environmental disasters.
Meteorology and Climatology: atmospheric pressure is measured in hectopascals (hPa) or millibars (mbar) in most countries worldwide. The US uses inches of mercury (inHg). Standard atmospheric pressure is 1013.25 hPa = 1013.25 mbar = 29.92 inHg = 760 mmHg. Pressure changes affect weather, hurricane forecasting, aviation safety. International meteorological data exchange requires accurate conversion.
Construction and Engineering: water supply is designed considering pressure of 2.5-6 bar (36-87 PSI) for normal operation. Low-pressure gas pipelines operate at 0.005-0.1 bar, medium pressure at 0.1-0.3 bar, high pressure above 0.3 bar. Hydraulic testing of pipelines is conducted at pressure 1.5-2 times higher than working pressure. Different building codes use different pressure units.
Physical Fundamentals of Pressure and Its Measurement
Pressure Definition: pressure is a physical quantity characterizing the intensity of normal forces exerted by liquid, gas, or solid on a unit surface area. Mathematically, pressure is defined as P = F/S, where F is force acting perpendicular to surface, S is surface area. Pressure is a scalar quantity and acts equally in all directions at each point in liquid or gas (Pascal's law).
Absolute and Relative Pressure: absolute pressure is measured relative to absolute vacuum (zero pressure). Relative (gauge) pressure is measured relative to atmospheric pressure. Vacuum pressure shows how much pressure is below atmospheric. Relationship: P_abs = P_gauge + P_atm, where P_atm ≈ 101.325 kPa at sea level. Understanding the difference is critically important for correct instrument reading interpretation.
Hydrostatic Pressure: liquid pressure at depth h is determined by formula P = ρgh + P₀, where ρ is liquid density, g is gravitational acceleration, P₀ is surface pressure. For water: every 33 feet (10 meters) of depth adds approximately 14.7 PSI (1 bar). This principle is used in liquid column manometers, barometers, for calculating pressure in tanks.
Atmospheric Pressure: created by atmospheric air weight and decreases with altitude according to barometric formula. At sea level P₀ = 14.696 PSI (101.325 kPa), at 18,000 feet (5.5 km) pressure decreases by half. Atmospheric pressure changes affect manometer readings, measurement accuracy, barometric instrument operation. Standard atmosphere is used as calibration reference.
History of Pressure Unit Development
Torricelli and Barometer Invention: in 1643-1644, Italian physicist Evangelista Torricelli conducted his famous experiment proving atmospheric pressure existence and inventing the first barometer. He filled a glass tube over one meter long with mercury, covered it with his finger, and inverted it into a mercury vessel. Mercury dropped to 760 mm level, creating vacuum in the tube's upper part. This proved atmosphere exerts pressure equivalent to 760 mm mercury column.
Blaise Pascal and Hydrostatic Laws: French mathematician and physicist Blaise Pascal in 1647-1648 conducted experiments confirming Torricelli's discovery. He proved atmospheric pressure decreases with altitude by asking his brother-in-law Florin Périer to take measurements on Puy-de-Dôme mountain. Pascal formulated fundamental hydrostatic law: pressure is transmitted by liquid unchanged in all directions. The pressure unit in SI system is named in his honor.
Metric System Development: after French Revolution, metric system was created seeking to unify all measurement units. Pascal as pressure unit was introduced in 20th century within International System of Units (SI). Previously, various local units were used: millimeters of mercury, atmospheres, kilograms per square centimeter. Standardization was critically important for science and industry development.
Industrial Revolution and New Needs: steam engine development, hydraulic systems, and pneumatic equipment required new pressure units for practical use. Bar was introduced as convenient unit approximately equal to atmospheric pressure. PSI (pounds per square inch) became standard in English-speaking countries due to convenience for engineering calculations. Different industrial sectors developed their own pressure measurement traditions.
Modern Pressure Measurement Technologies
Digital Pressure Gauges: use piezoelectric, capacitive, or resistive sensors to convert mechanical pressure to electrical signal. Provide high accuracy (up to ±0.01% of full scale), fast response, digital processing and data transmission capability. Support multiple measurement units with automatic conversion. Essential in automated control systems, scientific research, precision measurements.
Smart Pressure Sensors: modern sensors include microprocessors for self-diagnostics, temperature compensation, characteristic linearization. Support digital communication protocols (HART, Foundation Fieldbus, Profibus), remote programming, data archiving. Can automatically detect deviations, signal malfunctions, adapt to changing operating conditions.
Vacuum Measurements: for high and ultra-high vacuum, special methods are used: ionization gauges (10⁻⁴ - 10⁻¹² torr), thermocouple gauges (10⁻³ - 1 torr), diaphragm gauges (1 - 1000 torr). Each type has its accuracy range and application. Vacuum technologies are critically important for semiconductor manufacturing, scientific research, space technology.
Calibration and Metrology: national metrological institutes maintain pressure standards with high accuracy. Primary standards are based on fundamental physical principles (mercury manometers, piston gauges). Secondary standards are calibrated against primary ones and used for working instrument verification. International metrological cooperation ensures measurement unity worldwide.
Use our professional pressure converter for quick and accurate conversion between any pressure units. The calculator works in real-time, ensures maximum calculation accuracy, and supports all major pressure measurement systems worldwide!