This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI,[1][2] because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.
1 atm = 1013.25 mbar = 1013.25 hPa = 7005101325000000000♠101325Pa exactly (commonly used in atmospheric meteorology, in oceanography and for pressures within liquids, or in the industry for pressures within containers of liquefied gas)
1 mmHg = 7002133322387415000♠133.322387415 Pa at 0 °C = 7002133322387415000♠133.322387415 N/m2 at 0 °C = 7002133322387415000♠133.322387415 kg·cm−1·s−2 at 0 °C
^Taylor, Barry N. (ed.). The International System of Units (SI)(PDF). Special Publication 330. Gaithersburg, Maryland: National Institute of Standards and Technology (NIST). 2001.