Do you need to convert pressure from bar to psi, from psi to bar, from pascals to bar, or between other units of measurement? This online pressure converter quickly converts the units most commonly used in technical, industrial, automotive, pneumatic, hydraulic, meteorological, and scientific applications.
You can enter a value in any field. The converter automatically calculates all the other units, keeping pascals, bar, psi, atmospheres, Torr, mmHg, and the main water-column and mercury-column units separate.
Online pressure converter
Enter a value in any pressure unit. All the other units are calculated automatically. You can use either a period or a comma as the decimal separator. Do not use thousands separators.
If the entered value is invalid, the field is highlighted and the other results are cleared.
How the pressure converter works
The converter uses the pascal as its internal reference unit. When you enter a value, it is first converted to pascals and then converted into all the other available pressure units.
You can enter the value directly in bar, psi, Pa, kPa, MPa, mbar, hPa, atm, Torr, mmHg, kgf/cm², mH₂O, cmH₂O, mmH₂O, inH₂O, or inHg. Conversion takes place automatically as you type.
Pascal, kPa and MPa
The pascal is the SI unit of pressure. One pascal equals one newton per square meter.
The kilopascal is used when expressing values in pascals would produce excessively large numbers. The megapascal is common in hydraulics, mechanics, materials science, and high-pressure specifications.
1 kPa = 1000 Pa
1 MPa = 1000 kPa
1 MPa = 10 bar
1 MPa = 1 N/mm²
Converting bar, millibar and hPa
Bar is widely used in industry, pneumatic and hydraulic systems, compressors, pumps, and tire pressure measurement.
The millibar and hectopascal represent the same pressure numerically. For this reason, the two converter fields always show the same value.
1 bar = 100000 Pa
1 bar = 100 kPa
1 bar = 1000 mbar
1 hPa = 1 mbar
Converting bar and psi
psi stands for pound-force per square inch and is a widely used pressure unit in countries that use imperial or U.S. customary units. It is common in specifications for tires, compressors, pneumatic tools, hydraulic systems, and industrial equipment.
The converter lets you convert directly from bar to psi or from psi to bar by entering a value in either field.
Standard atmosphere (atm)
The standard atmosphere is a conventionally defined reference pressure. It is used in physics, chemistry, thermodynamics, and many technical calculations.
1 atm = 101325 Pa
This value is a conventional reference and does not mean that actual atmospheric pressure is always the same. Air pressure varies with altitude, weather conditions, and measurement location.
Torricelli (Torr) and millimeters of mercury (mmHg)
The Torr is named after Evangelista Torricelli and is used mainly in vacuum applications, physics, and some scientific equipment. By definition, 760 Torr equals one standard atmosphere.
The millimeter of mercury (mmHg) historically derives from the pressure produced by a column of mercury. It is still widely used in some scientific and medical fields.
Torr and mmHg have extremely close values, but the converter keeps them separate by using their respective conventional definitions.
Kilogram-force per square centimeter (kgf/cm²)
The technically correct unit is kilogram-force per square centimeter (kgf/cm²). In practical use, it is often abbreviated as kg/cm².
This unit is still found on older pressure gauges, in technical documentation, industrial equipment, hydraulic systems, and machinery.
Water column: mH₂O, cmH₂O, mmH₂O and inH₂O
Water-column units are used to measure pressure and pressure differences. The meter of water (mH₂O) is particularly useful in hydraulics and pumping systems, and for expressing pump head. It is also useful for estimating pressure due to water depth, for example in pools, tanks, and the sea. Centimeters and millimeters of water are mainly used for lower pressures.
Water-column units are also common in ventilation, air conditioning, filters, fans, low-pressure pneumatic systems, and instrumentation.
The converter uses conventional values for mH₂O, cmH₂O, mmH₂O, and inH₂O. A real liquid column can produce slightly different values depending on density, temperature, and local gravitational acceleration.
1 mH₂O = 9806.65 Pa
1 mH₂O = 0.0980665 bar
Inch of mercury (inHg)
The inch of mercury (inHg) is used mainly in meteorology, aviation, vacuum applications, and English-language technical documentation.
The converter uses the conventional inHg value to provide consistent and repeatable conversions.
Absolute pressure and gauge pressure
Unit conversion should not be confused with conversion between absolute pressure and gauge pressure.
Absolute pressure uses absolute vacuum as its reference. Gauge pressure uses the atmospheric pressure at the measurement point as its reference.
The converter changes only the unit of measurement and does not automatically add or subtract atmospheric pressure. To convert gauge pressure to absolute pressure, you need to know the reference atmospheric pressure.
For this reason, designations such as bar(a), bar(g), psia, and psig must be interpreted correctly before performing the calculation.
The converter also accepts negative values, which are useful for expressing vacuum or gauge pressures below atmospheric pressure. Absolute pressure, however, cannot be negative.
Tire pressure in bar and psi
One of the most common uses of bar-to-psi conversion is for the tires of cars, motorcycles, bicycles, and other vehicles.
The converter quickly converts a value from bar to psi or from psi to bar. To determine the correct tire pressure, always use the values specified by the vehicle or tire manufacturer.
Pressure in pneumatic and hydraulic systems
In pneumatic systems, bar is one of the most common units, while U.S. technical documentation often uses psi. MPa and psi are also used in high-pressure hydraulic systems.
The meter of water is particularly useful for pumps and hydraulic systems because it allows pressure to be compared directly with pump head expressed as a height of water column.
The converter therefore lets you quickly compare data from sensors, pressure gauges, pumps, compressors, valves, control units, and technical documentation that use different units.
Atmospheric pressure and meteorology
In meteorology, atmospheric pressure is commonly expressed in hectopascals (hPa). The millibar (mbar) is also widely used historically and has the same numerical value as the hectopascal.
Some English-language equipment and technical documentation use inches of mercury (inHg) instead. The converter lets you compare these units directly.
Pressure units available in the converter
The calculator converts Pascal (Pa), Hectopascal (hPa), Kilopascal (kPa), Megapascal (MPa), Bar (bar), Millibar (mbar), Pound-force per square inch (psi), Standard atmosphere (atm), Torricelli (Torr), Millimeter of mercury (mmHg), Kilogram-force per square centimeter (kgf/cm²), Meter of water (mH₂O), Centimeter of water (cmH₂O), Millimeter of water (mmH₂O), Inch of water (inH₂O), and Inch of mercury (inHg).
Technical conversion references
The conversion factors used by the calculator are based on SI unit references and conventional technical conversion values.
One bar is exactly 100000 Pa, and one standard atmosphere is exactly 101325 Pa. The Torr is defined as 1/760 of a standard atmosphere.
Conventional values are used for units based on water and mercury columns, avoiding dependence on temperature, fluid density, and local gravity.