Bar (unit) 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 bar and the millibar were introduced by the Norwegian meteorologist Vilhelm Bjerknes, who was a founder of the modern practice of weather forecasting. The International Bureau of Weights and Measures (BIPM) lists the bar as one of the "non-SI units [that authors] should have the freedom to use", but has declined to
Equivalent air depth depth is governed by Pascal's law: Using the SI system with pressures expressed in pascal, we have: Expressing the pressures in atmospheres yields a convenient formula (1 atm ≡ 101325 Pa): To simplify the algebra we will define formula_12. Combining the general formula and Pascal's law, we have: so that Since formula_15, the equivalent formula for the imperial system becomes Substituting R again, and noting that formula_17, we have the concrete formulas: Although not all dive tables are recommended for use in this way, the Bühlmann tables are suitable for use with these kind of calculations. At 27 metres the