| millimetre of mercury | |
|---|---|
| Unit of | Pressure |
| Symbol | mmHg, mm Hg |
| Conversions | |
| 1 mmHg in ... | ... is equal to ... |
| SI units | 133.322 Pa |
| English Engineering units | 0.01933678 lbf/in2 |
A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly 133.322387415 pascals[1] or approximately 133.322 pascals.[2] It is denoted mmHg[3] or mm Hg.[4][2]
Although not an SI unit, the millimetre of mercury is still often encountered in some fields; for example, it is still widely used in medicine, as demonstrated for example in the medical literature indexed in PubMed.[5] For example, the U.S. and European guidelines on hypertension, in using millimeters of mercury for blood pressure,[6] are reflecting the fact (common basic knowledge among health care professionals) that this is the usual unit of blood pressure in clinical medicine.
One millimetre of mercury is approximately 1 torr, which is 1/760 of standard atmospheric pressure (101325/760 ≈ 133.322368421 pascals). Although the two units are not equal, the relative difference (less than 0.000015%) is negligible for most practical uses.
- ^ BS 350: Part 1: 1974 – Conversion factors and tables. British Standards Institution. 1974. p. 49.
- ^ a b Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC of the European Economic Community
- ^ 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 2021-06-04, retrieved 2021-12-16
- ^ "AMA Manual of Style Online". American Medical Association. Retrieved 2018-02-24.
- ^ National Center for Biotechnology Information of the National Library of Medicine of the United States. "Articles demonstrating pressures in mm Hg". PubMed. Retrieved 2023-09-02.
- ^ Gijón-Conde, T; Sánchez-Martínez, M; Graciani, A; Cruz, JJ; López-García, E; Ortolá, R; Rodríguez-Artalejo, F; Banegas, JR (July 2019). "Impact of the European and American guidelines on hypertension prevalence, treatment, and cardiometabolic goals". Journal of Hypertension. 37 (7): 1393–1400. doi:10.1097/HJH.0000000000002065. PMID 31145710. S2CID 86674318.