# Hydrostatic Pressure

## 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

*. The pressure acting in water at*

*1000 kg/m*^{3}*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

*. The pressure acting in water at*

*1.940 slugs/ft*^{3}*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)*