Pressure Unit Converter

Common Pressure Conversions

Understanding Pressure Units

Pressure is defined as force per unit area. It is a fundamental physical quantity used across science, engineering, meteorology, and medicine. The SI unit of pressure is the pascal (Pa), defined as one newton per square meter. Because one pascal is a very small pressure, kilopascals (kPa), bars, and atmospheres are more commonly used in everyday applications.

SI and Metric Units

• Pascal (Pa): The SI derived unit of pressure. Equal to one newton per square meter (N/m2). Named after Blaise Pascal, the French mathematician and physicist.
• Hectopascal (hPa): Equal to 100 Pa. The standard unit used in meteorology for reporting atmospheric pressure. Numerically equal to the millibar.
• Kilopascal (kPa): Equal to 1,000 Pa. Commonly used for tire pressure in most countries and in engineering specifications.
• Megapascal (MPa): Equal to 1,000,000 Pa. Used for high-pressure applications such as material strength testing, hydraulic systems, and geology.
• Bar (bar): Equal to exactly 100,000 Pa. Widely used in industry, meteorology, and scuba diving. Roughly equal to atmospheric pressure at sea level.
• Millibar (mbar): Equal to 0.001 bar or 100 Pa. Identical to the hectopascal. Historically the primary unit in meteorology before the adoption of hPa.

Atmosphere Units

• Standard Atmosphere (atm): Defined as exactly 101,325 Pa. Represents the average atmospheric pressure at sea level at 15 degrees C. Used as a reference in chemistry, aviation, and diving.
• Technical Atmosphere (at): Defined as one kilogram-force per square centimeter (kgf/cm2), equal to 98,066.5 Pa. Historically used in some European engineering standards.

Mercury and Manometric Units

• Torr (Torr): Approximately equal to 1 mmHg. Named after Evangelista Torricelli, inventor of the mercury barometer. Defined as exactly 1/760 of a standard atmosphere (133.32237 Pa).
• Millimeter of Mercury (mmHg): The pressure exerted by a 1 mm column of mercury at 0 degrees C under standard gravity. Equal to 133.322 Pa. Standard unit for blood pressure measurement and vacuum systems.
• Inch of Mercury (inHg): Equal to 25.4 mmHg or 3,386.39 Pa. Used in aviation altimetry and US weather reporting for barometric pressure.
• Centimeter of Water (cmH2O): The pressure exerted by a 1 cm column of water at 4 degrees C. Equal to 98.0665 Pa. Used in medical ventilation and low-pressure measurement.
• Inch of Water (inH2O): Equal to 249.089 Pa. Used in HVAC systems, clean room pressurization, and duct pressure measurements.

Imperial and Engineering Units

• Pound per Square Inch (PSI): Equal to 6,894.76 Pa. The most common pressure unit in the United States. Used for tire pressure, compressed gas, and hydraulic systems.
• Kilopound per Square Inch (ksi): Equal to 1,000 PSI or 6,894,757 Pa. Used in material science for tensile strength and structural engineering.
• Pound per Square Foot (psf): Equal to 1/144 PSI or 47.8803 Pa. Used in structural engineering for floor loads, wind pressure, and soil bearing capacity.

Practical Applications

Standard Pressure Values

References

The conversion factors used in this calculator are based on internationally recognized standards and authoritative sources:

• BIPM - SI Derived Units (International Bureau of Weights and Measures)
• NIST - The International System of Units (SI)
• NIST - Approximate Conversions from Metric to US Customary Measures
• ISO 2533:1975 - Standard Atmosphere
• World Meteorological Organization - Guide to Meteorological Instruments and Methods of Observation

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