Pounds per square inch (psi) is a crucial unit of pressure measurement, widely used across various industries, including automotive, aviation, and even space exploration. One interesting fact is that a typical car tire is inflated to around 30 psi, but did you know that a commercial jetliner’s cabin is pressurized to a reduced level of 11 psi to simulate being at a comfortable altitude of about 6,000-8,000 feet? This helps passengers avoid the stress of low oxygen levels while flying at over 35,000 feet, where the atmospheric pressure is a meager 4 psi.
Moreover, psi is pivotal in assessing the force exerted on surfaces. If you’ve ever wondered why deep-sea submarines have thick hulls, it’s because they must withstand pressures of around 8,800 psi at depths of 6 miles beneath the ocean’s surface! This ensures safe exploration of the mysterious deep-sea world, showcasing psi’s significance in enabling human feats in extreme environments.
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.
Pounds per square inch | Millimeters of mercury |
---|---|
0
psi
|
0
mmHg
|
10
psi
|
517.15096
mmHg
|
20
psi
|
1034.30192
mmHg
|
30
psi
|
1551.45287
mmHg
|
40
psi
|
2068.60383
mmHg
|
50
psi
|
2585.75479
mmHg
|
60
psi
|
3102.90575
mmHg
|
70
psi
|
3620.05671
mmHg
|
80
psi
|
4137.20766
mmHg
|
90
psi
|
4654.35862
mmHg
|
100
psi
|
5171.50958
mmHg
|
110
psi
|
5688.66054
mmHg
|
120
psi
|
6205.81149
mmHg
|
130
psi
|
6722.96245
mmHg
|
140
psi
|
7240.11341
mmHg
|
150
psi
|
7757.26437
mmHg
|
160
psi
|
8274.41533
mmHg
|
170
psi
|
8791.56628
mmHg
|
180
psi
|
9308.71724
mmHg
|
190
psi
|
9825.8682
mmHg
|
200
psi
|
10343.01916
mmHg
|
210
psi
|
10860.17012
mmHg
|
220
psi
|
11377.32107
mmHg
|
230
psi
|
11894.47203
mmHg
|
240
psi
|
12411.62299
mmHg
|
250
psi
|
12928.77395
mmHg
|
260
psi
|
13445.9249
mmHg
|
270
psi
|
13963.07586
mmHg
|
280
psi
|
14480.22682
mmHg
|
290
psi
|
14997.37778
mmHg
|
300
psi
|
15514.52874
mmHg
|
310
psi
|
16031.67969
mmHg
|
320
psi
|
16548.83065
mmHg
|
330
psi
|
17065.98161
mmHg
|
340
psi
|
17583.13257
mmHg
|
350
psi
|
18100.28353
mmHg
|
360
psi
|
18617.43448
mmHg
|
370
psi
|
19134.58544
mmHg
|
380
psi
|
19651.7364
mmHg
|
390
psi
|
20168.88736
mmHg
|
400
psi
|
20686.03831
mmHg
|
410
psi
|
21203.18927
mmHg
|
420
psi
|
21720.34023
mmHg
|
430
psi
|
22237.49119
mmHg
|
440
psi
|
22754.64215
mmHg
|
450
psi
|
23271.7931
mmHg
|
460
psi
|
23788.94406
mmHg
|
470
psi
|
24306.09502
mmHg
|
480
psi
|
24823.24598
mmHg
|
490
psi
|
25340.39694
mmHg
|
500
psi
|
25857.54789
mmHg
|
510
psi
|
26374.69885
mmHg
|
520
psi
|
26891.84981
mmHg
|
530
psi
|
27409.00077
mmHg
|
540
psi
|
27926.15172
mmHg
|
550
psi
|
28443.30268
mmHg
|
560
psi
|
28960.45364
mmHg
|
570
psi
|
29477.6046
mmHg
|
580
psi
|
29994.75556
mmHg
|
590
psi
|
30511.90651
mmHg
|
600
psi
|
31029.05747
mmHg
|
610
psi
|
31546.20843
mmHg
|
620
psi
|
32063.35939
mmHg
|
630
psi
|
32580.51035
mmHg
|
640
psi
|
33097.6613
mmHg
|
650
psi
|
33614.81226
mmHg
|
660
psi
|
34131.96322
mmHg
|
670
psi
|
34649.11418
mmHg
|
680
psi
|
35166.26513
mmHg
|
690
psi
|
35683.41609
mmHg
|
700
psi
|
36200.56705
mmHg
|
710
psi
|
36717.71801
mmHg
|
720
psi
|
37234.86897
mmHg
|
730
psi
|
37752.01992
mmHg
|
740
psi
|
38269.17088
mmHg
|
750
psi
|
38786.32184
mmHg
|
760
psi
|
39303.4728
mmHg
|
770
psi
|
39820.62376
mmHg
|
780
psi
|
40337.77471
mmHg
|
790
psi
|
40854.92567
mmHg
|
800
psi
|
41372.07663
mmHg
|
810
psi
|
41889.22759
mmHg
|
820
psi
|
42406.37854
mmHg
|
830
psi
|
42923.5295
mmHg
|
840
psi
|
43440.68046
mmHg
|
850
psi
|
43957.83142
mmHg
|
860
psi
|
44474.98238
mmHg
|
870
psi
|
44992.13333
mmHg
|
880
psi
|
45509.28429
mmHg
|
890
psi
|
46026.43525
mmHg
|
900
psi
|
46543.58621
mmHg
|
910
psi
|
47060.73717
mmHg
|
920
psi
|
47577.88812
mmHg
|
930
psi
|
48095.03908
mmHg
|
940
psi
|
48612.19004
mmHg
|
950
psi
|
49129.341
mmHg
|
960
psi
|
49646.49196
mmHg
|
970
psi
|
50163.64291
mmHg
|
980
psi
|
50680.79387
mmHg
|
990
psi
|
51197.94483
mmHg
|
1000
psi
|
51715.09579
mmHg
|
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