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.
The megapascal (MPa) is a unit of pressure that is often used in a variety of scientific and engineering calculations, especially in materials science. One fascinating aspect of the megapascal is how it bridges different disciplines, such as geology, where it helps measure the strength of rocks, and civil engineering, where it is crucial for understanding the stress in structures. Interestingly, 1 MPa is equivalent to the pressure exerted by a weight of about 10.2 metric tons on a single square meter, illustrating its significant impact compared to everyday pressures we encounter.
In the realm of meteorology, pressures measured in MPa can indicate catastrophic weather conditions, as atmospheric pressure is usually measured in hectorpascals due to its lower scale. Also noteworthy is the use of MPa in automotive engine performance, where it assesses combustion forces, underlying the importance of this unit in ensuring both vehicle efficiency and safety. Thus, the megapascal is vital across varied fields, reflecting the diverse applications of pressure measurement in modern technology and natural phenomena.
Inches of mercury | Megapascals |
---|---|
0
inHg
|
0
MPa
|
1
inHg
|
0.00338639
MPa
|
2
inHg
|
0.00677278
MPa
|
3
inHg
|
0.0101592
MPa
|
4
inHg
|
0.0135456
MPa
|
5
inHg
|
0.0169319
MPa
|
6
inHg
|
0.0203183
MPa
|
7
inHg
|
0.0237047
MPa
|
8
inHg
|
0.0270911
MPa
|
9
inHg
|
0.0304775
MPa
|
10
inHg
|
0.0338639
MPa
|
11
inHg
|
0.0372503
MPa
|
12
inHg
|
0.0406367
MPa
|
13
inHg
|
0.0440231
MPa
|
14
inHg
|
0.0474094
MPa
|
15
inHg
|
0.0507958
MPa
|
16
inHg
|
0.0541822
MPa
|
17
inHg
|
0.0575686
MPa
|
18
inHg
|
0.060955
MPa
|
19
inHg
|
0.0643414
MPa
|
20
inHg
|
0.0677278
MPa
|
21
inHg
|
0.0711142
MPa
|
22
inHg
|
0.0745006
MPa
|
23
inHg
|
0.0778869
MPa
|
24
inHg
|
0.0812733
MPa
|
25
inHg
|
0.0846597
MPa
|
26
inHg
|
0.0880461
MPa
|
27
inHg
|
0.0914325
MPa
|
28
inHg
|
0.0948189
MPa
|
29
inHg
|
0.0982053
MPa
|
30
inHg
|
0.101592
MPa
|
31
inHg
|
0.104978
MPa
|
32
inHg
|
0.108364
MPa
|
33
inHg
|
0.111751
MPa
|
34
inHg
|
0.115137
MPa
|
35
inHg
|
0.118524
MPa
|
36
inHg
|
0.12191
MPa
|
37
inHg
|
0.125296
MPa
|
38
inHg
|
0.128683
MPa
|
39
inHg
|
0.132069
MPa
|
40
inHg
|
0.135456
MPa
|
41
inHg
|
0.138842
MPa
|
42
inHg
|
0.142228
MPa
|
43
inHg
|
0.145615
MPa
|
44
inHg
|
0.149001
MPa
|
45
inHg
|
0.152388
MPa
|
46
inHg
|
0.155774
MPa
|
47
inHg
|
0.15916
MPa
|
48
inHg
|
0.162547
MPa
|
49
inHg
|
0.165933
MPa
|
50
inHg
|
0.169319
MPa
|
51
inHg
|
0.172706
MPa
|
52
inHg
|
0.176092
MPa
|
53
inHg
|
0.179479
MPa
|
54
inHg
|
0.182865
MPa
|
55
inHg
|
0.186251
MPa
|
56
inHg
|
0.189638
MPa
|
57
inHg
|
0.193024
MPa
|
58
inHg
|
0.196411
MPa
|
59
inHg
|
0.199797
MPa
|
60
inHg
|
0.203183
MPa
|
61
inHg
|
0.20657
MPa
|
62
inHg
|
0.209956
MPa
|
63
inHg
|
0.213343
MPa
|
64
inHg
|
0.216729
MPa
|
65
inHg
|
0.220115
MPa
|
66
inHg
|
0.223502
MPa
|
67
inHg
|
0.226888
MPa
|
68
inHg
|
0.230274
MPa
|
69
inHg
|
0.233661
MPa
|
70
inHg
|
0.237047
MPa
|
71
inHg
|
0.240434
MPa
|
72
inHg
|
0.24382
MPa
|
73
inHg
|
0.247206
MPa
|
74
inHg
|
0.250593
MPa
|
75
inHg
|
0.253979
MPa
|
76
inHg
|
0.257366
MPa
|
77
inHg
|
0.260752
MPa
|
78
inHg
|
0.264138
MPa
|
79
inHg
|
0.267525
MPa
|
80
inHg
|
0.270911
MPa
|
81
inHg
|
0.274298
MPa
|
82
inHg
|
0.277684
MPa
|
83
inHg
|
0.28107
MPa
|
84
inHg
|
0.284457
MPa
|
85
inHg
|
0.287843
MPa
|
86
inHg
|
0.291229
MPa
|
87
inHg
|
0.294616
MPa
|
88
inHg
|
0.298002
MPa
|
89
inHg
|
0.301389
MPa
|
90
inHg
|
0.304775
MPa
|
91
inHg
|
0.308161
MPa
|
92
inHg
|
0.311548
MPa
|
93
inHg
|
0.314934
MPa
|
94
inHg
|
0.318321
MPa
|
95
inHg
|
0.321707
MPa
|
96
inHg
|
0.325093
MPa
|
97
inHg
|
0.32848
MPa
|
98
inHg
|
0.331866
MPa
|
99
inHg
|
0.335253
MPa
|
100
inHg
|
0.338639
MPa
|
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