The millimeter of mercury (mmHg) is a unit of pressure traditionally used in medicine and meteorology, and its history dates back to the barometer invention by Evangelista Torricelli in 1643. Often, it is associated with measuring blood pressure and intraocular pressure, representing the pressure exerted by a column of mercury precisely 1 millimeter high. This fascinating unit highlights the interplay of physics and medicine, reflecting both the force of blood circulating against vessel walls and the atmospheric pressure’s effects on our weather systems.
Interestingly, mmHg is one of the few units still officially sanctioned for use with SI (International System of Units) under specific legal and medical contexts, underscoring its importance over centuries. Despite the global shift towards using Pascals for pressure, mmHg remains ingrained in clinical settings because of its historical usage and direct relation to human physiology. Its origins and continued use illustrate how historical scientific instruments still influence modern practices.
The millibar, a unit of pressure, traces its origins back to the 1800s when it was introduced by the meteorologists Henry H. Hilderbrandsson and Vagn Walfrid Ekman. Used primarily in meteorology, the millibar found its place in daily weather reports around the world. Measuring atmospheric pressure in thousands, one millibar equates to 100 pascals in the SI system, providing a convenient scale for understanding variations in atmospheric conditions.
Intriguingly, the typical sea-level atmospheric pressure is about 1013 millibars. This is the weight of the air around us, controlled by a delicate balance of gases and climatic factors. During severe weather events, such as hurricanes, the central pressure can drastically drop to around 920 millibars, signifying powerful winds and storms. This makes the millibar not just a scientific measure, but a crucial tool for predicting and understanding weather patterns.
| Millimeters of mercury | Millibar |
|---|---|
0
mmHg
|
0
mbar
|
10
mmHg
|
13.3322
mbar
|
20
mmHg
|
26.6644
mbar
|
30
mmHg
|
39.9966
mbar
|
40
mmHg
|
53.3288
mbar
|
50
mmHg
|
66.661
mbar
|
60
mmHg
|
79.9932
mbar
|
70
mmHg
|
93.3254
mbar
|
80
mmHg
|
106.6576
mbar
|
90
mmHg
|
119.9898
mbar
|
100
mmHg
|
133.322
mbar
|
110
mmHg
|
146.6542
mbar
|
120
mmHg
|
159.9864
mbar
|
130
mmHg
|
173.3186
mbar
|
140
mmHg
|
186.6508
mbar
|
150
mmHg
|
199.983
mbar
|
160
mmHg
|
213.3152
mbar
|
170
mmHg
|
226.6474
mbar
|
180
mmHg
|
239.9796
mbar
|
190
mmHg
|
253.3118
mbar
|
200
mmHg
|
266.644
mbar
|
210
mmHg
|
279.9762
mbar
|
220
mmHg
|
293.3084
mbar
|
230
mmHg
|
306.6406
mbar
|
240
mmHg
|
319.9728
mbar
|
250
mmHg
|
333.305
mbar
|
260
mmHg
|
346.6372
mbar
|
270
mmHg
|
359.9694
mbar
|
280
mmHg
|
373.3016
mbar
|
290
mmHg
|
386.6338
mbar
|
300
mmHg
|
399.966
mbar
|
310
mmHg
|
413.2982
mbar
|
320
mmHg
|
426.6304
mbar
|
330
mmHg
|
439.9626
mbar
|
340
mmHg
|
453.2948
mbar
|
350
mmHg
|
466.627
mbar
|
360
mmHg
|
479.9592
mbar
|
370
mmHg
|
493.2914
mbar
|
380
mmHg
|
506.6236
mbar
|
390
mmHg
|
519.9558
mbar
|
400
mmHg
|
533.288
mbar
|
410
mmHg
|
546.6202
mbar
|
420
mmHg
|
559.9524
mbar
|
430
mmHg
|
573.2846
mbar
|
440
mmHg
|
586.6168
mbar
|
450
mmHg
|
599.949
mbar
|
460
mmHg
|
613.2812
mbar
|
470
mmHg
|
626.6134
mbar
|
480
mmHg
|
639.9456
mbar
|
490
mmHg
|
653.2778
mbar
|
500
mmHg
|
666.61
mbar
|
510
mmHg
|
679.9422
mbar
|
520
mmHg
|
693.2744
mbar
|
530
mmHg
|
706.6066
mbar
|
540
mmHg
|
719.9388
mbar
|
550
mmHg
|
733.271
mbar
|
560
mmHg
|
746.6032
mbar
|
570
mmHg
|
759.9354
mbar
|
580
mmHg
|
773.2676
mbar
|
590
mmHg
|
786.5998
mbar
|
600
mmHg
|
799.932
mbar
|
610
mmHg
|
813.2642
mbar
|
620
mmHg
|
826.5964
mbar
|
630
mmHg
|
839.9286
mbar
|
640
mmHg
|
853.2608
mbar
|
650
mmHg
|
866.593
mbar
|
660
mmHg
|
879.9252
mbar
|
670
mmHg
|
893.2574
mbar
|
680
mmHg
|
906.5896
mbar
|
690
mmHg
|
919.9218
mbar
|
700
mmHg
|
933.254
mbar
|
710
mmHg
|
946.5862
mbar
|
720
mmHg
|
959.9184
mbar
|
730
mmHg
|
973.2506
mbar
|
740
mmHg
|
986.5828
mbar
|
750
mmHg
|
999.915
mbar
|
760
mmHg
|
1013.2472
mbar
|
770
mmHg
|
1026.5794
mbar
|
780
mmHg
|
1039.9116
mbar
|
790
mmHg
|
1053.2438
mbar
|
800
mmHg
|
1066.576
mbar
|
810
mmHg
|
1079.9082
mbar
|
820
mmHg
|
1093.2404
mbar
|
830
mmHg
|
1106.5726
mbar
|
840
mmHg
|
1119.9048
mbar
|
850
mmHg
|
1133.237
mbar
|
860
mmHg
|
1146.5692
mbar
|
870
mmHg
|
1159.9014
mbar
|
880
mmHg
|
1173.2336
mbar
|
890
mmHg
|
1186.5658
mbar
|
900
mmHg
|
1199.898
mbar
|
910
mmHg
|
1213.2302
mbar
|
920
mmHg
|
1226.5624
mbar
|
930
mmHg
|
1239.8946
mbar
|
940
mmHg
|
1253.2268
mbar
|
950
mmHg
|
1266.559
mbar
|
960
mmHg
|
1279.8912
mbar
|
970
mmHg
|
1293.2234
mbar
|
980
mmHg
|
1306.5556
mbar
|
990
mmHg
|
1319.8878
mbar
|
1000
mmHg
|
1333.22
mbar
|
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