The hectopascal (hPa) is a commonly used unit for measuring atmospheric pressure, especially in meteorology. One hPa is equivalent to 100 pascals, making it a preferred measurement over pascals due to the convenient scale. Interestingly, 1 hPa is also equivalent to 1 millibar, a unit that was widely used before the adoption of the hectopascal. This equivalence makes it easy for transitioning instruments and readings in weather maps and reports.
Hectopascals play a crucial role in understanding atmospheric conditions, such as weather forecasting and studying phenomena like hurricanes or cyclones. Typically, sea-level pressure is around 1013 hPa, and deviations from this can indicate changing weather patterns, with lower pressures often associated with storm systems. This connection makes the hPa unit vital for predicting and understanding weather events globally.
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.
Hectopascals | Millimeters of mercury |
---|---|
0
hPa
|
0
mmHg
|
10
hPa
|
7.50064
mmHg
|
20
hPa
|
15.00128
mmHg
|
30
hPa
|
22.50191
mmHg
|
40
hPa
|
30.00255
mmHg
|
50
hPa
|
37.50319
mmHg
|
60
hPa
|
45.00383
mmHg
|
70
hPa
|
52.50446
mmHg
|
80
hPa
|
60.0051
mmHg
|
90
hPa
|
67.50574
mmHg
|
100
hPa
|
75.00638
mmHg
|
110
hPa
|
82.50701
mmHg
|
120
hPa
|
90.00765
mmHg
|
130
hPa
|
97.50829
mmHg
|
140
hPa
|
105.00893
mmHg
|
150
hPa
|
112.50956
mmHg
|
160
hPa
|
120.0102
mmHg
|
170
hPa
|
127.51084
mmHg
|
180
hPa
|
135.01148
mmHg
|
190
hPa
|
142.51211
mmHg
|
200
hPa
|
150.01275
mmHg
|
210
hPa
|
157.51339
mmHg
|
220
hPa
|
165.01403
mmHg
|
230
hPa
|
172.51466
mmHg
|
240
hPa
|
180.0153
mmHg
|
250
hPa
|
187.51594
mmHg
|
260
hPa
|
195.01658
mmHg
|
270
hPa
|
202.51721
mmHg
|
280
hPa
|
210.01785
mmHg
|
290
hPa
|
217.51849
mmHg
|
300
hPa
|
225.01913
mmHg
|
310
hPa
|
232.51976
mmHg
|
320
hPa
|
240.0204
mmHg
|
330
hPa
|
247.52104
mmHg
|
340
hPa
|
255.02168
mmHg
|
350
hPa
|
262.52231
mmHg
|
360
hPa
|
270.02295
mmHg
|
370
hPa
|
277.52359
mmHg
|
380
hPa
|
285.02423
mmHg
|
390
hPa
|
292.52486
mmHg
|
400
hPa
|
300.0255
mmHg
|
410
hPa
|
307.52614
mmHg
|
420
hPa
|
315.02678
mmHg
|
430
hPa
|
322.52741
mmHg
|
440
hPa
|
330.02805
mmHg
|
450
hPa
|
337.52869
mmHg
|
460
hPa
|
345.02933
mmHg
|
470
hPa
|
352.52997
mmHg
|
480
hPa
|
360.0306
mmHg
|
490
hPa
|
367.53124
mmHg
|
500
hPa
|
375.03188
mmHg
|
510
hPa
|
382.53252
mmHg
|
520
hPa
|
390.03315
mmHg
|
530
hPa
|
397.53379
mmHg
|
540
hPa
|
405.03443
mmHg
|
550
hPa
|
412.53507
mmHg
|
560
hPa
|
420.0357
mmHg
|
570
hPa
|
427.53634
mmHg
|
580
hPa
|
435.03698
mmHg
|
590
hPa
|
442.53762
mmHg
|
600
hPa
|
450.03825
mmHg
|
610
hPa
|
457.53889
mmHg
|
620
hPa
|
465.03953
mmHg
|
630
hPa
|
472.54017
mmHg
|
640
hPa
|
480.0408
mmHg
|
650
hPa
|
487.54144
mmHg
|
660
hPa
|
495.04208
mmHg
|
670
hPa
|
502.54272
mmHg
|
680
hPa
|
510.04335
mmHg
|
690
hPa
|
517.54399
mmHg
|
700
hPa
|
525.04463
mmHg
|
710
hPa
|
532.54527
mmHg
|
720
hPa
|
540.0459
mmHg
|
730
hPa
|
547.54654
mmHg
|
740
hPa
|
555.04718
mmHg
|
750
hPa
|
562.54782
mmHg
|
760
hPa
|
570.04845
mmHg
|
770
hPa
|
577.54909
mmHg
|
780
hPa
|
585.04973
mmHg
|
790
hPa
|
592.55037
mmHg
|
800
hPa
|
600.051
mmHg
|
810
hPa
|
607.55164
mmHg
|
820
hPa
|
615.05228
mmHg
|
830
hPa
|
622.55292
mmHg
|
840
hPa
|
630.05355
mmHg
|
850
hPa
|
637.55419
mmHg
|
860
hPa
|
645.05483
mmHg
|
870
hPa
|
652.55547
mmHg
|
880
hPa
|
660.0561
mmHg
|
890
hPa
|
667.55674
mmHg
|
900
hPa
|
675.05738
mmHg
|
910
hPa
|
682.55802
mmHg
|
920
hPa
|
690.05865
mmHg
|
930
hPa
|
697.55929
mmHg
|
940
hPa
|
705.05993
mmHg
|
950
hPa
|
712.56057
mmHg
|
960
hPa
|
720.06121
mmHg
|
970
hPa
|
727.56184
mmHg
|
980
hPa
|
735.06248
mmHg
|
990
hPa
|
742.56312
mmHg
|
1000
hPa
|
750.06376
mmHg
|
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