Millimeter of mercury - wikipedia Millimeter of mercury A millimeter of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high and now defined as precisely 7002133322387415000 ♠ 133.322 387 415 pascals. It is denoted by the symbol mmHg or mm Hg. Although not an SI unit, the millimeter of mercury is still routinely used in medicine, meteorology, aviation, and many other scientific fields. One millimeter of mercury is approximately 1 Torr, which is 1 / 760 of standard atmospheric pressure ( 7005101325000000000 ♠ 101 325 / 760 = 7002133322368421053 ♠ 133.322 368 421 053 pascals ). The two units are not exactly equal ; however, the relative difference ( less than 0.000 015 % ) is negligible for most practical uses. Contents 1 History and definition 2 Relation to the torr 3 Use in medicine and physiology 4 See also 5 References History and definition Further information : pressure head Mercury manometers were the first accurate pressure gauges ; they are less used today due to mercury 's toxicity, the mercury column 's sensitivity to temperature and local gravity, and the greater convenience of other instrumentation. They displayed the pressure difference between two fluids as a vertical difference between the mercury levels in two connected reservoirs. An actual mercury column reading may be converted to more fundamental units of pressure by multiplying the difference in height between two mercury levels by the density of mercury and the local gravitational acceleration. Because the density of mercury depends on temperature and surface gravity, both of which vary with local conditions, specific standard values for these two parameters were adopted. This resulted in defining a `` millimeter of mercury '' as the pressure exerted at the base of a column of mercury 1 millimeter high with a precise density of 13595.1 kg / m when the acceleration due to gravity is exactly 9.80665 m / s. The density 13595.1 kg / m chosen for this definition is the approximate density of mercury at 0 ° C ( 32 ° F ), and 9.80665 m / s is standard gravity. The use of an actual column of mercury to measure pressure normally requires correction for the density of mercury at the actual temperature and the sometimes marked variation of gravity with location, and may be further corrected to take account of the density of the measured air, water or other fluid. Relation to the torr The precision of modern transducers is often insufficient to show the difference between the torr and the millimetre of mercury. The torr is about one part in seven million or 0.000 015 % less. Use in medicine and physiology In medicine, pressure is still generally measured in millimeters of mercury. These measurements are in general given relative to the current atmospheric pressure : for example, a blood pressure of 120 mmHg, when the current atmospheric pressure is 760 mmHg, means 880 mmHg relative to perfect vacuum. Routine pressure measurements in medicine include : Blood pressure, measured with a sphygmomanometer Intraocular pressure, with a tonometer Cerebrospinal fluid pressure Intracranial pressure Intramuscular pressure ( compartment syndrome ) Central venous pressure Pulmonary artery catheterization Mechanical ventilation In physiology manometric units are used to measure Starling forces. Pressure units Pascal Bar Technical atmosphere Standard atmosphere Torr Pounds per square inch ( Pa ) ( bar ) ( at ) ( atm ) ( Torr ) ( lbf / in ) 1 Pa ≡ 1 N / m 10 6995101970000000000 ♠ 1.0197 × 10 6994986919999999999 ♠ 9.8692 × 10 6997750060000000000 ♠ 7.5006 × 10 6996145037700000000 ♠ 1.450 377 × 10 1 bar 10 ≡ 100 kPa ≡ 10 dyn / cm 7000101970000000000 ♠ 1.0197 6999986920000000000 ♠ 0.986 92 7002750060000000000 ♠ 750.06 7001145037700000000 ♠ 14.503 77 1 at 7004980665000000000 ♠ 9.806 65 × 10 6999980665000000000 ♠ 0.980 665 ≡ 1 kgf / cm 6999967841100000000 ♠ 0.967 8411 7002735559200000000 ♠ 735.5592 7001142233400000000 ♠ 14.223 34 1 atm 7005101325000000000 ♠ 1.013 25 × 10 7000101325000000000 ♠ 1.013 25 7000103319999999999 ♠ 1.0332 ≡ 7002760000000000000 ♠ 760 7001146959500000000 ♠ 14.695 95 1 Torr 7002133322399999999 ♠ 133.3224 6997133322400000000 ♠ 1.333 224 × 10 6997135955100000000 ♠ 1.359 551 × 10 ≡ 1 / 760 ≈ 6997131578900000000 ♠ 1.315 789 × 10 ≡ 1 Torr ≈ 1 mmHg 6998193367800000000 ♠ 1.933 678 × 10 1 lbf / in 7003689480000000000 ♠ 6.8948 × 10 6998689480000000000 ♠ 6.8948 × 10 6998703069000000000 ♠ 7.030 69 × 10 6998680460000000000 ♠ 6.8046 × 10 7001517149300000000 ♠ 51.714 93 ≡ 1 lbf / in See also Inch of mercury Inch of water Pound per square inch Bar ( unit ) Torr References Jump up ^ BS 350 : Part 1 : 1974 -- Conversion factors and tables. British Standards Institution. 1974. p. 49. Jump up ^ International Bureau of Weights and Measures ( 2006 ), The International System of Units ( SI ) ( PDF ) ( 8th ed. ), p. 127, ISBN 92 - 822 - 2213 - 6, archived ( PDF ) from the original on 2017 - 08 - 14 Jump up ^ American Medical Association, AMA Manual of Style Online, retrieved 2018 - 02 - 24. Jump up ^ Kaye, G.W.C. ; Laby, T.H. ( 1986 ). Tables of Physical and Chemical Constants ( XV ed. ). Longman. pp. 22 -- 23. ISBN 0582463548. Jump up ^ `` Pressure Units ''. National Physical Laboratory ( NPL ). Retrieved 25 January 2015. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Millimeter_of_mercury&oldid=840911830 '' Categories : Units of pressure Mercury ( element ) Talk Contents About Wikipedia Беларуская ( тарашкевіца ) ‎ Български Bosanski Deutsch Español فارسی Français Galego 한국어 Հայերեն Hrvatski Latviešu Македонски Nederlands 日本 語 Norsk Norsk nynorsk Português Русский Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska ไทย Türkçe Українська 粵語 中文 21 more Edit links This page was last edited on 12 May 2018, at 22 : 26. About Wikipedia

Question: the value of pressure represented by 1 mm of hg
Answer: 133.322387415 pascals