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.
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.
| Millibar | Millimeters of mercury |
|---|---|
0
mbar
|
0
mmHg
|
10
mbar
|
7.50064
mmHg
|
20
mbar
|
15.00128
mmHg
|
30
mbar
|
22.50191
mmHg
|
40
mbar
|
30.00255
mmHg
|
50
mbar
|
37.50319
mmHg
|
60
mbar
|
45.00383
mmHg
|
70
mbar
|
52.50446
mmHg
|
80
mbar
|
60.0051
mmHg
|
90
mbar
|
67.50574
mmHg
|
100
mbar
|
75.00638
mmHg
|
110
mbar
|
82.50701
mmHg
|
120
mbar
|
90.00765
mmHg
|
130
mbar
|
97.50829
mmHg
|
140
mbar
|
105.00893
mmHg
|
150
mbar
|
112.50956
mmHg
|
160
mbar
|
120.0102
mmHg
|
170
mbar
|
127.51084
mmHg
|
180
mbar
|
135.01148
mmHg
|
190
mbar
|
142.51211
mmHg
|
200
mbar
|
150.01275
mmHg
|
210
mbar
|
157.51339
mmHg
|
220
mbar
|
165.01403
mmHg
|
230
mbar
|
172.51466
mmHg
|
240
mbar
|
180.0153
mmHg
|
250
mbar
|
187.51594
mmHg
|
260
mbar
|
195.01658
mmHg
|
270
mbar
|
202.51721
mmHg
|
280
mbar
|
210.01785
mmHg
|
290
mbar
|
217.51849
mmHg
|
300
mbar
|
225.01913
mmHg
|
310
mbar
|
232.51976
mmHg
|
320
mbar
|
240.0204
mmHg
|
330
mbar
|
247.52104
mmHg
|
340
mbar
|
255.02168
mmHg
|
350
mbar
|
262.52231
mmHg
|
360
mbar
|
270.02295
mmHg
|
370
mbar
|
277.52359
mmHg
|
380
mbar
|
285.02423
mmHg
|
390
mbar
|
292.52486
mmHg
|
400
mbar
|
300.0255
mmHg
|
410
mbar
|
307.52614
mmHg
|
420
mbar
|
315.02678
mmHg
|
430
mbar
|
322.52741
mmHg
|
440
mbar
|
330.02805
mmHg
|
450
mbar
|
337.52869
mmHg
|
460
mbar
|
345.02933
mmHg
|
470
mbar
|
352.52997
mmHg
|
480
mbar
|
360.0306
mmHg
|
490
mbar
|
367.53124
mmHg
|
500
mbar
|
375.03188
mmHg
|
510
mbar
|
382.53252
mmHg
|
520
mbar
|
390.03315
mmHg
|
530
mbar
|
397.53379
mmHg
|
540
mbar
|
405.03443
mmHg
|
550
mbar
|
412.53507
mmHg
|
560
mbar
|
420.0357
mmHg
|
570
mbar
|
427.53634
mmHg
|
580
mbar
|
435.03698
mmHg
|
590
mbar
|
442.53762
mmHg
|
600
mbar
|
450.03825
mmHg
|
610
mbar
|
457.53889
mmHg
|
620
mbar
|
465.03953
mmHg
|
630
mbar
|
472.54017
mmHg
|
640
mbar
|
480.0408
mmHg
|
650
mbar
|
487.54144
mmHg
|
660
mbar
|
495.04208
mmHg
|
670
mbar
|
502.54272
mmHg
|
680
mbar
|
510.04335
mmHg
|
690
mbar
|
517.54399
mmHg
|
700
mbar
|
525.04463
mmHg
|
710
mbar
|
532.54527
mmHg
|
720
mbar
|
540.0459
mmHg
|
730
mbar
|
547.54654
mmHg
|
740
mbar
|
555.04718
mmHg
|
750
mbar
|
562.54782
mmHg
|
760
mbar
|
570.04845
mmHg
|
770
mbar
|
577.54909
mmHg
|
780
mbar
|
585.04973
mmHg
|
790
mbar
|
592.55037
mmHg
|
800
mbar
|
600.051
mmHg
|
810
mbar
|
607.55164
mmHg
|
820
mbar
|
615.05228
mmHg
|
830
mbar
|
622.55292
mmHg
|
840
mbar
|
630.05355
mmHg
|
850
mbar
|
637.55419
mmHg
|
860
mbar
|
645.05483
mmHg
|
870
mbar
|
652.55547
mmHg
|
880
mbar
|
660.0561
mmHg
|
890
mbar
|
667.55674
mmHg
|
900
mbar
|
675.05738
mmHg
|
910
mbar
|
682.55802
mmHg
|
920
mbar
|
690.05865
mmHg
|
930
mbar
|
697.55929
mmHg
|
940
mbar
|
705.05993
mmHg
|
950
mbar
|
712.56057
mmHg
|
960
mbar
|
720.06121
mmHg
|
970
mbar
|
727.56184
mmHg
|
980
mbar
|
735.06248
mmHg
|
990
mbar
|
742.56312
mmHg
|
1000
mbar
|
750.06376
mmHg
|
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