Available Pressure units

• pascal conversions

  The pascal is the SI base unit of pressure, equal to one newton per square metre. It is used in meteorology, fluid dynamics, materials science, and all scientific pressure measurements.

• kilopascal conversions

  A kilopascal is a metric pressure unit equal to 1,000 pascals. It is used for weather forecasts, tire pressure specifications in metric countries, and structural and mechanical engineering calculations.

• bar conversions

  A bar is a pressure unit approximately equal to standard atmospheric pressure, or 100,000 pascals. It is widely used in meteorology, hydraulics, diving equipment, and industrial pressure gauges.

• pound per square inch conversions

  Pound per square inch (psi) is an imperial pressure unit widely used in the United States for tire inflation, hydraulic system pressures, gas cylinder ratings, and plumbing specifications.

• atmosphere conversions

  An atmosphere (atm) is a pressure unit equal to mean atmospheric pressure at sea level, approximately 101,325 pascals. It is used as a reference in chemistry, diving tables, and altitude calculations.

• millibar conversions

  A millibar is a pressure unit equal to one thousandth of a bar. It is the standard unit for atmospheric pressure in meteorology and weather forecasting, particularly in aviation and marine contexts.

• hectopascal conversions

  A hectopascal is a pressure unit equal to 100 pascals, numerically identical to the millibar. It is the standard unit for atmospheric pressure reports in modern meteorology and aviation weather data.

• torr conversions

  A torr is a pressure unit equal to approximately 1/760 of an atmosphere. It is used in vacuum technology, low-pressure experimental physics, and blood pressure measurement in older clinical literature.

• inch of mercury conversions

  Inch of mercury (inHg) is a pressure unit representing the pressure exerted by a one-inch column of mercury. It is used in aviation altimetry, barometric pressure readings, and vacuum measurements in the United States.

• megapascal conversions

  A megapascal is a pressure unit equal to one million pascals. It is used for measuring high pressures in industrial hydraulics, structural materials testing, and deep-sea and geological applications.

Full Pressure conversion matrix

About Pressure

Units of pressure

Real-world uses

Pressure measurement is critical in meteorology, medicine, engineering, and diving. Weather forecasters track atmospheric pressure in hectopascals to predict storms. Blood pressure is still universally reported in millimetres of mercury (mmHg). Tyre pressure is specified in PSI or bar depending on the region. Industrial hydraulic systems operate at hundreds of bar, and vacuum chambers for semiconductor manufacturing require pressures measured in millipascals.

History

Evangelista Torricelli invented the mercury barometer in 1643, demonstrating that atmospheric pressure supports a column of mercury about 760 mm high. Blaise Pascal subsequently showed that pressure decreases with altitude, lending his name to the SI unit. The standard atmosphere (101,325 Pa) was established as a reference in the early 20th century. Daniel Bernoulli's 1738 work on fluid dynamics connected pressure to velocity, laying the foundation for modern aerodynamics.

Common mistakes

A common error is confusing absolute pressure with gauge pressure — a tyre inflated to "32 PSI" is actually at about 46.7 PSI absolute (32 + 14.7 atmospheric). People also mistakenly equate bar and atmosphere: 1 bar is 100,000 Pa, while 1 atm is 101,325 Pa — close but not identical. Another frequent mistake is treating torr and mmHg as exactly the same; they differ by less than 0.000015%, but in high-precision work this matters.

Measurement standards

The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.

Did you know?

The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.

Common values