Hydrostatic Pressure vs. Depth
Depth and hydrostatic pressure.
Hydrostatic pressure in a liquid can be calculated as
p = ρ g h (1)
where
p = pressure in liquid (N/m ^{ 2 } , Pa, lb _{ f } /ft ^{ 2 } , psf)
ρ = density of liquid (kg/m ^{ 3 } , slugs /ft ^{ 3 } )
g = acceleration of gravity (9.81 m/s ^{ 2 } , 32.17405 ft/s ^{ 2 } )
h = height of fluid column  or depth in the fluid where pressure is measured (m, ft)
Hydrostatic pressure in a water column  or depth ( density of water 1000 kg/m ^{ 3 } ):
Height of Water Column  Pressure  

(m)  (ft)  (kPa)  (bar)  (atm)  (psi) 
1  3.28  9.81  0.098  0.097  1.42 
2  6.56  19.6  0.196  0.194  2.85 
3  9.84  29.4  0.294  0.290  4.27 
4  13.1  39.2  0.392  0.387  5.69 
5  16.4  49.1  0.491  0.484  7.11 
6  19.7  58.9  0.589  0.581  8.54 
7  23.0  68.7  0.687  0.678  10.0 
8  26.2  78.5  0.785  0.775  11.4 
9  29.5  88.3  0.883  0.871  12.8 
10  32.8  98.1  0.981  0.968  14.2 
12  39.4  118  1.18  1.16  17.1 
14  45.9  137  1.37  1.36  19.9 
16  52.5  157  1.57  1.55  22.8 
18  59.0  177  1.77  1.74  25.6 
20  65.6  196  1.96  1.94  28.5 
25  82.0  245  2.45  2.42  35.6 
30  98.4  294  2.94  2.90  42.7 
35  115  343  3.43  3.39  49.8 
40  131  392  3.92  3.87  56.9 
50  164  491  4.91  4.84  71.1 
60  197  589  5.89  5.81  85.4 
70  230  687  6.87  6.78  100 
80  262  785  7.85  7.75  114 
90  295  883  8.83  8.71  128 
100  328  981  9.81  9.68  142 
Example  Pressure acting in water at depth 1 m
The density of water at 4 ^{ o } C is 1000 kg/m ^{ 3 } . The pressure acting in water at 1 m can be calculated as
p = ρ g h
= ( 1000 kg/m ^{ 3 } ) ( 9.81 m/s ^{ 2 } ) (1 m)
= 9810 Pa
Example  Pressure acting in water at depth 3 ft
The density of water at 32 ^{ o } F is 1.940 slugs/ft ^{ 3 } . The pressure acting in water at 3 ft can be calculated as
p = ρ g h
= ( 1.940 slugs/ft ^{ 3 } ) ( 32.17405 ft/s ^{ 2 } ) (3 ft)
= 187.3 lb _{ f } /ft ^{ 2 } (psf)
= 1.3 lb _{ f } /in ^{ 2 } (psi)
Ocean Pressure  Depth and Latitude
Ocean pressure varies with depth and position (latitude) on earth.
Depth (m)  Ocean Pressure (MPa)  

Latitude (degrees)  
0  15  30  45  60  75  90  
0  0  0  0  0  0  0  0 
1000  10.080  10.083  10.093  10.106  10.120  10.130  10.133 
2000  20.208  20.215  20.234  20.261  20.288  20.308  20.315 
3000  30.383  30.394  30.424  30.464  30.505  30.535  30.545 
4000  40.606  40.620  40.660  40.714  40.768  40.808  40.823 
5000  50.874  50.892  50.942  51.010  51.079  51.129  51.147 
6000  61.188  61.210  61.270  61.352  61.434  61.495  61.517 
7000  71.547  71.572  71.643  71.739  71.835  71.906  71.932 
8000  81.949  81.979  82.059  82.170  82.280  82.361  82.391 
9000  92.395  92.428  92.519  92.644  92.769  92.861  92.894 
10000  102.880  102.917  103.019  103.157  103.296  103.398  103.436 
 1 Pa = 10 ^{ 6 } MPa = 10 ^{ 3 } kPa = 10 ^{ 6 } N/mm ^{ 2 } = 10 ^{ 5 } bar = 0.1020 kp/m ^{ 2 } = 1.020x10 ^{ 4 } m H _{ 2 } O at 4°C/39°F = 9.869x10 ^{ 6 } atm = 0.004 in H _{ 2 } O= 1.450x10 ^{ 4 } psi (lbf/in ^{ 2 } ) = 0.02089 lbf/ft ^{ 2 } (psf)
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