Bar (unit) The kilobar, equivalent to 100 MPa, is commonly used in geological systems, particularly in experimental petrology. "Bar(a)" and "bara" are sometimes used to indicate absolute pressures and "bar(g)" and "barg" for gauge pressures. This usage is deprecated and fuller descriptions such as "gauge pressure of 2 bar" or "2-bar gauge" are recommended. Bar (unit) The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa, which is slightly less than the current average atmospheric pressure on Earth at sea level. The
Pressure Pressure is distributed to solid boundaries or across arbitrary sections of fluid "normal to" these boundaries or sections at every point. It is a fundamental parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N/m, or kg·m·s). This name for the unit was added in 1971; before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch and bar, are also in common use. The CGS unit of pressure is the barye