Pascal (unit) Pascal (unit) The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa) which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa) which is equal to one centibar. The unit of measurement called standard atmosphere (atm) is defined as . Meteorological reports typically state atmospheric pressure in millibars. The unit is
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