The torr is a unit of pressure named after the Italian physicist Evangelista Torricelli, who invented the barometer in the 17th century. It is defined as 1/760th of an atmosphere, approximating the pressure exerted by a one-millimeter column of mercury at 0 degrees Celsius. What makes the torr particularly interesting is its practical use in fields like vacuum technology and weather forecasting, where precise measurements of atmospheric pressure are crucial.
The legacy of Torricelli’s work is integral to meteorology and physics, as it opened paths for understanding atmospheric pressure. Beyond scientific circles, the torr is a reminder of human ingenuity in unraveling atmospheric mysteries and continues to play a vital role in today’s scientific advancements.
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.
Torr | Inches of mercury |
---|---|
0
torr
|
0
inHg
|
10
torr
|
0.393701
inHg
|
20
torr
|
0.787401
inHg
|
30
torr
|
1.1811
inHg
|
40
torr
|
1.5748
inHg
|
50
torr
|
1.9685
inHg
|
60
torr
|
2.3622
inHg
|
70
torr
|
2.7559
inHg
|
80
torr
|
3.14961
inHg
|
90
torr
|
3.54331
inHg
|
100
torr
|
3.93701
inHg
|
110
torr
|
4.33071
inHg
|
120
torr
|
4.72441
inHg
|
130
torr
|
5.11811
inHg
|
140
torr
|
5.51181
inHg
|
150
torr
|
5.90551
inHg
|
160
torr
|
6.29921
inHg
|
170
torr
|
6.69291
inHg
|
180
torr
|
7.08661
inHg
|
190
torr
|
7.48031
inHg
|
200
torr
|
7.87401
inHg
|
210
torr
|
8.26771
inHg
|
220
torr
|
8.66142
inHg
|
230
torr
|
9.05512
inHg
|
240
torr
|
9.44882
inHg
|
250
torr
|
9.84252
inHg
|
260
torr
|
10.23622
inHg
|
270
torr
|
10.62992
inHg
|
280
torr
|
11.02362
inHg
|
290
torr
|
11.41732
inHg
|
300
torr
|
11.81102
inHg
|
310
torr
|
12.20472
inHg
|
320
torr
|
12.59842
inHg
|
330
torr
|
12.99212
inHg
|
340
torr
|
13.38582
inHg
|
350
torr
|
13.77952
inHg
|
360
torr
|
14.17323
inHg
|
370
torr
|
14.56693
inHg
|
380
torr
|
14.96063
inHg
|
390
torr
|
15.35433
inHg
|
400
torr
|
15.74803
inHg
|
410
torr
|
16.14173
inHg
|
420
torr
|
16.53543
inHg
|
430
torr
|
16.92913
inHg
|
440
torr
|
17.32283
inHg
|
450
torr
|
17.71653
inHg
|
460
torr
|
18.11023
inHg
|
470
torr
|
18.50393
inHg
|
480
torr
|
18.89763
inHg
|
490
torr
|
19.29133
inHg
|
500
torr
|
19.68503
inHg
|
510
torr
|
20.07874
inHg
|
520
torr
|
20.47244
inHg
|
530
torr
|
20.86614
inHg
|
540
torr
|
21.25984
inHg
|
550
torr
|
21.65354
inHg
|
560
torr
|
22.04724
inHg
|
570
torr
|
22.44094
inHg
|
580
torr
|
22.83464
inHg
|
590
torr
|
23.22834
inHg
|
600
torr
|
23.62204
inHg
|
610
torr
|
24.01574
inHg
|
620
torr
|
24.40944
inHg
|
630
torr
|
24.80314
inHg
|
640
torr
|
25.19684
inHg
|
650
torr
|
25.59055
inHg
|
660
torr
|
25.98425
inHg
|
670
torr
|
26.37795
inHg
|
680
torr
|
26.77165
inHg
|
690
torr
|
27.16535
inHg
|
700
torr
|
27.55905
inHg
|
710
torr
|
27.95275
inHg
|
720
torr
|
28.34645
inHg
|
730
torr
|
28.74015
inHg
|
740
torr
|
29.13385
inHg
|
750
torr
|
29.52755
inHg
|
760
torr
|
29.92125
inHg
|
770
torr
|
30.31495
inHg
|
780
torr
|
30.70865
inHg
|
790
torr
|
31.10235
inHg
|
800
torr
|
31.49606
inHg
|
810
torr
|
31.88976
inHg
|
820
torr
|
32.28346
inHg
|
830
torr
|
32.67716
inHg
|
840
torr
|
33.07086
inHg
|
850
torr
|
33.46456
inHg
|
860
torr
|
33.85826
inHg
|
870
torr
|
34.25196
inHg
|
880
torr
|
34.64566
inHg
|
890
torr
|
35.03936
inHg
|
900
torr
|
35.43306
inHg
|
910
torr
|
35.82676
inHg
|
920
torr
|
36.22046
inHg
|
930
torr
|
36.61416
inHg
|
940
torr
|
37.00787
inHg
|
950
torr
|
37.40157
inHg
|
960
torr
|
37.79527
inHg
|
970
torr
|
38.18897
inHg
|
980
torr
|
38.58267
inHg
|
990
torr
|
38.97637
inHg
|
1000
torr
|
39.37007
inHg
|
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