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.
A “meter of water @ 4°C” is a unique unit used primarily to measure pressure. At this specific temperature, water reaches its maximum density, and the pressure exerted by a one-meter column of water is approximately 9.81 kilopascals or 0.0979 atmospheres. This scenario represents the optimal conditions for standardizing pressure measurements because the physical properties of water are most stable, reducing variances in calculations.
This unit is especially important in fields like plumbing and hydraulics, where accurate pressure measurements are crucial. Understanding these principles can lead to better designs in water distribution systems, preventing common issues such as pipe bursts or inefficient water flow, ensuring systems operate safely and efficiently.
| Millimeters of mercury | Meters of water @ 4°C |
|---|---|
0
mmHg
|
0
mH₂O
|
10
mmHg
|
0.135951
mH₂O
|
20
mmHg
|
0.271901
mH₂O
|
30
mmHg
|
0.407852
mH₂O
|
40
mmHg
|
0.543802
mH₂O
|
50
mmHg
|
0.679753
mH₂O
|
60
mmHg
|
0.815704
mH₂O
|
70
mmHg
|
0.951654
mH₂O
|
80
mmHg
|
1.0876
mH₂O
|
90
mmHg
|
1.22356
mH₂O
|
100
mmHg
|
1.35951
mH₂O
|
110
mmHg
|
1.49546
mH₂O
|
120
mmHg
|
1.63141
mH₂O
|
130
mmHg
|
1.76736
mH₂O
|
140
mmHg
|
1.90331
mH₂O
|
150
mmHg
|
2.03926
mH₂O
|
160
mmHg
|
2.17521
mH₂O
|
170
mmHg
|
2.31116
mH₂O
|
180
mmHg
|
2.44711
mH₂O
|
190
mmHg
|
2.58306
mH₂O
|
200
mmHg
|
2.71901
mH₂O
|
210
mmHg
|
2.85496
mH₂O
|
220
mmHg
|
2.99091
mH₂O
|
230
mmHg
|
3.12686
mH₂O
|
240
mmHg
|
3.26281
mH₂O
|
250
mmHg
|
3.39877
mH₂O
|
260
mmHg
|
3.53472
mH₂O
|
270
mmHg
|
3.67067
mH₂O
|
280
mmHg
|
3.80662
mH₂O
|
290
mmHg
|
3.94257
mH₂O
|
300
mmHg
|
4.07852
mH₂O
|
310
mmHg
|
4.21447
mH₂O
|
320
mmHg
|
4.35042
mH₂O
|
330
mmHg
|
4.48637
mH₂O
|
340
mmHg
|
4.62232
mH₂O
|
350
mmHg
|
4.75827
mH₂O
|
360
mmHg
|
4.89422
mH₂O
|
370
mmHg
|
5.03017
mH₂O
|
380
mmHg
|
5.16612
mH₂O
|
390
mmHg
|
5.30207
mH₂O
|
400
mmHg
|
5.43802
mH₂O
|
410
mmHg
|
5.57397
mH₂O
|
420
mmHg
|
5.70993
mH₂O
|
430
mmHg
|
5.84588
mH₂O
|
440
mmHg
|
5.98183
mH₂O
|
450
mmHg
|
6.11778
mH₂O
|
460
mmHg
|
6.25373
mH₂O
|
470
mmHg
|
6.38968
mH₂O
|
480
mmHg
|
6.52563
mH₂O
|
490
mmHg
|
6.66158
mH₂O
|
500
mmHg
|
6.79753
mH₂O
|
510
mmHg
|
6.93348
mH₂O
|
520
mmHg
|
7.06943
mH₂O
|
530
mmHg
|
7.20538
mH₂O
|
540
mmHg
|
7.34133
mH₂O
|
550
mmHg
|
7.47728
mH₂O
|
560
mmHg
|
7.61323
mH₂O
|
570
mmHg
|
7.74918
mH₂O
|
580
mmHg
|
7.88514
mH₂O
|
590
mmHg
|
8.02109
mH₂O
|
600
mmHg
|
8.15704
mH₂O
|
610
mmHg
|
8.29299
mH₂O
|
620
mmHg
|
8.42894
mH₂O
|
630
mmHg
|
8.56489
mH₂O
|
640
mmHg
|
8.70084
mH₂O
|
650
mmHg
|
8.83679
mH₂O
|
660
mmHg
|
8.97274
mH₂O
|
670
mmHg
|
9.10869
mH₂O
|
680
mmHg
|
9.24464
mH₂O
|
690
mmHg
|
9.38059
mH₂O
|
700
mmHg
|
9.51654
mH₂O
|
710
mmHg
|
9.65249
mH₂O
|
720
mmHg
|
9.78844
mH₂O
|
730
mmHg
|
9.92439
mH₂O
|
740
mmHg
|
10.06034
mH₂O
|
750
mmHg
|
10.1963
mH₂O
|
760
mmHg
|
10.33225
mH₂O
|
770
mmHg
|
10.4682
mH₂O
|
780
mmHg
|
10.60415
mH₂O
|
790
mmHg
|
10.7401
mH₂O
|
800
mmHg
|
10.87605
mH₂O
|
810
mmHg
|
11.012
mH₂O
|
820
mmHg
|
11.14795
mH₂O
|
830
mmHg
|
11.2839
mH₂O
|
840
mmHg
|
11.41985
mH₂O
|
850
mmHg
|
11.5558
mH₂O
|
860
mmHg
|
11.69175
mH₂O
|
870
mmHg
|
11.8277
mH₂O
|
880
mmHg
|
11.96365
mH₂O
|
890
mmHg
|
12.0996
mH₂O
|
900
mmHg
|
12.23555
mH₂O
|
910
mmHg
|
12.37151
mH₂O
|
920
mmHg
|
12.50746
mH₂O
|
930
mmHg
|
12.64341
mH₂O
|
940
mmHg
|
12.77936
mH₂O
|
950
mmHg
|
12.91531
mH₂O
|
960
mmHg
|
13.05126
mH₂O
|
970
mmHg
|
13.18721
mH₂O
|
980
mmHg
|
13.32316
mH₂O
|
990
mmHg
|
13.45911
mH₂O
|
1000
mmHg
|
13.59506
mH₂O
|
If you like the website, share it on social media.