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 “inch of mercury” (inHg) is a unit of pressure commonly used in aviation, meteorology, and refrigeration. It originates from the barometric pressure measurement practice using a column of mercury. This unit became a staple due to its early adoption in weather forecasting and its accurate and consistent measurements. An interesting fact is that an inch of mercury is approximately equal to 33.86 millibars or 3386 Pascals, but what truly distinguishes it is its historical significance in the development of modern atmospheric science.
In the 17th century, Evangelista Torricelli, a student of Galileo, first discovered that atmospheric pressure could sustain a column of mercury, laying the groundwork for this unit. His invention, the barometer, revolutionized how we understand and predict weather, marking the inch of mercury as more than just a unit—it’s a nod to the evolution of scientific inquiry and practice.
Pounds per square inch | Inches of mercury |
---|---|
0
psi
|
0
inHg
|
10
psi
|
20.36021
inHg
|
20
psi
|
40.72043
inHg
|
30
psi
|
61.08064
inHg
|
40
psi
|
81.44085
inHg
|
50
psi
|
101.80106
inHg
|
60
psi
|
122.16128
inHg
|
70
psi
|
142.52149
inHg
|
80
psi
|
162.8817
inHg
|
90
psi
|
183.24192
inHg
|
100
psi
|
203.60213
inHg
|
110
psi
|
223.96234
inHg
|
120
psi
|
244.32255
inHg
|
130
psi
|
264.68277
inHg
|
140
psi
|
285.04298
inHg
|
150
psi
|
305.40319
inHg
|
160
psi
|
325.76341
inHg
|
170
psi
|
346.12362
inHg
|
180
psi
|
366.48383
inHg
|
190
psi
|
386.84404
inHg
|
200
psi
|
407.20426
inHg
|
210
psi
|
427.56447
inHg
|
220
psi
|
447.92468
inHg
|
230
psi
|
468.2849
inHg
|
240
psi
|
488.64511
inHg
|
250
psi
|
509.00532
inHg
|
260
psi
|
529.36554
inHg
|
270
psi
|
549.72575
inHg
|
280
psi
|
570.08596
inHg
|
290
psi
|
590.44617
inHg
|
300
psi
|
610.80639
inHg
|
310
psi
|
631.1666
inHg
|
320
psi
|
651.52681
inHg
|
330
psi
|
671.88703
inHg
|
340
psi
|
692.24724
inHg
|
350
psi
|
712.60745
inHg
|
360
psi
|
732.96766
inHg
|
370
psi
|
753.32788
inHg
|
380
psi
|
773.68809
inHg
|
390
psi
|
794.0483
inHg
|
400
psi
|
814.40852
inHg
|
410
psi
|
834.76873
inHg
|
420
psi
|
855.12894
inHg
|
430
psi
|
875.48915
inHg
|
440
psi
|
895.84937
inHg
|
450
psi
|
916.20958
inHg
|
460
psi
|
936.56979
inHg
|
470
psi
|
956.93001
inHg
|
480
psi
|
977.29022
inHg
|
490
psi
|
997.65043
inHg
|
500
psi
|
1018.01064
inHg
|
510
psi
|
1038.37086
inHg
|
520
psi
|
1058.73107
inHg
|
530
psi
|
1079.09128
inHg
|
540
psi
|
1099.4515
inHg
|
550
psi
|
1119.81171
inHg
|
560
psi
|
1140.17192
inHg
|
570
psi
|
1160.53213
inHg
|
580
psi
|
1180.89235
inHg
|
590
psi
|
1201.25256
inHg
|
600
psi
|
1221.61277
inHg
|
610
psi
|
1241.97299
inHg
|
620
psi
|
1262.3332
inHg
|
630
psi
|
1282.69341
inHg
|
640
psi
|
1303.05362
inHg
|
650
psi
|
1323.41384
inHg
|
660
psi
|
1343.77405
inHg
|
670
psi
|
1364.13426
inHg
|
680
psi
|
1384.49448
inHg
|
690
psi
|
1404.85469
inHg
|
700
psi
|
1425.2149
inHg
|
710
psi
|
1445.57511
inHg
|
720
psi
|
1465.93533
inHg
|
730
psi
|
1486.29554
inHg
|
740
psi
|
1506.65575
inHg
|
750
psi
|
1527.01597
inHg
|
760
psi
|
1547.37618
inHg
|
770
psi
|
1567.73639
inHg
|
780
psi
|
1588.09661
inHg
|
790
psi
|
1608.45682
inHg
|
800
psi
|
1628.81703
inHg
|
810
psi
|
1649.17724
inHg
|
820
psi
|
1669.53746
inHg
|
830
psi
|
1689.89767
inHg
|
840
psi
|
1710.25788
inHg
|
850
psi
|
1730.6181
inHg
|
860
psi
|
1750.97831
inHg
|
870
psi
|
1771.33852
inHg
|
880
psi
|
1791.69873
inHg
|
890
psi
|
1812.05895
inHg
|
900
psi
|
1832.41916
inHg
|
910
psi
|
1852.77937
inHg
|
920
psi
|
1873.13959
inHg
|
930
psi
|
1893.4998
inHg
|
940
psi
|
1913.86001
inHg
|
950
psi
|
1934.22022
inHg
|
960
psi
|
1954.58044
inHg
|
970
psi
|
1974.94065
inHg
|
980
psi
|
1995.30086
inHg
|
990
psi
|
2015.66108
inHg
|
1000
psi
|
2036.02129
inHg
|
If you like the website, share it on social media.