Calculate pressure from head and specific gravity, or find total head or specific gravity using ft, m, in and psi, bar, kPa, or MPa.

Convert fluid head to an equivalent pressure difference.

Uses density = SG ร— 1,000 kg/mยณ and standard gravity 9.80665 m/sยฒ. Signed values represent pressure/head differences; this does not add atmospheric pressure.

1 is the nominal water reference. Use your fluidโ€™s density divided by 1,000 kg/mยณ.

Pressure From Head Formula

The following formula is used to calculate the Pressure From Head. 

P(psi) โ‰ˆ 0.433527504 ร— H(ft) ร— SG
  • Where P is the Pressure From Head (psi)
  • H is the equivalent fluid pressure head (ft) 
  • SG is the specific gravity 

To calculate pressure difference from head, use ฮ”p = ฯgH. This calculator uses ฯ = SG ร— 1,000 kg/mยณ and standard gravity g = 9.80665 m/sยฒ, giving approximately 0.433527504 psi per foot for SG = 1. The result is a pressure difference; atmospheric pressure is not added.

Feet of Head to Pressure Conversion Table (Specific Gravity, SG = 1.00)
Head (ft) Pressure (psi) bar kPa MPa
10.4340.0302.9890.003
20.8670.0605.9780.006
31.3010.0908.9670.009
41.7340.12011.9560.012
52.1680.14914.9450.015
62.6010.17917.9340.018
83.4680.23923.9130.024
104.3350.29929.8910.030
125.2020.35935.8690.036
156.5030.44844.8360.045
208.6710.59859.7810.060
2510.8380.74774.7270.075
3013.0060.89789.6720.090
4017.3411.196119.5630.120
5021.6761.495149.4530.149
6026.0121.793179.3440.179
8034.6822.391239.1250.239
10043.3532.989298.9070.299
15065.0294.484448.3600.448
20086.7065.978597.8130.598
* Rounded to 3 decimals. Assumes SG = 1.00 with a nominal reference density of 1,000 kg/mยณ and g = 9.80665 m/sยฒ. P(Pa) = 1,000 ร— 9.80665 ร— H(m). Actual water density varies with temperature. Unit conversions: 1 psi โ‰ˆ 6.894757293 kPa; 1 bar = 100 kPa; 1 MPa = 1,000 kPa.

How to Calculate Pressure From Head?

The following two example problems outline how to calculate the Pressure From Head.

Example Problem #1:

  1. First, determine the total head (ft). In this example, the total head (ft) is given as 1235.
  2. Next, determine the specific gravity. For this problem, the specific gravity is given as 0.85.
  3. Finally, calculate the Pressure From Head using the equation above: 

P(psi) โ‰ˆ 0.433527504 ร— H(ft) ร— SG

Inserting the values from above and solving the equation with the imputed values gives: 

P โ‰ˆ 0.433527504 ร— 1235 ร— 0.85 โ‰ˆ 455.0955 psi

Example Problem #2: 

Using the same process as above, first define the variables required by the formula. In this case, these values are:

total head (ft) = 55

specific gravity = 1.2

Entering these values yields:

P โ‰ˆ 0.433527504 ร— 55 ร— 1.2 โ‰ˆ 28.6128 psi