# Converting pump head to pressure

### How to convert a pressure to a pump head ?

1. Introduction
2. Converting a pump head to a pressure
3. Converting a pressure to a pump head
4.Change of head and pressure with the liquid density
5. Manufacturers
6. Free Excel calculation tool to convert head to pressure

## 1. Introduction

Pump manufacturers are typically referring to pump head to define the performance of their pumps. However, Process Engineers very often need to reuse the pump head for further calculation, to determine the flow rate or the pressure drop in a pipe, it is then necessary to convert the pump head to a pressure unit such as bar or psi.

## 2. Converting a pump head to a pressure

Having a pump characteristic in m, it is possible to define the pressure in Pa by using the following formula :

P = ρ.g.H

With :

P = pressure (Pa)
ρ = density of the fluid pumped (kg/m3)
g = gravity acceleration = 9.81 m.s-2

To have the value in bar, divide by 100000 : P=ρ.g.H/100000

Example

A pump is giving a head of 20 m, the fluid process is water at 25c which has a specific gravity of 999 kg/m3

P = 999*9.81*20 = 196003.8 Pa or 1.96 bar

## 3. Converting a pressure to a pump head

It is basically the calculation above but in the reverse direction

H = P / (ρ.g)

With :

P = pressure (Pa)
ρ = density of the fluid pumped (kg/m3)
g = gravity acceleration = 9.81 m.s-2

If the pressure is in bar, multiply by 100000 : H = P*100000 / (ρ.g)

## 4. Change of head and pressure with the liquid density

What is important to highlight is that the pump, if run with the same impeller and same speed, will develop the same head whatever the liquid that is used. That is why manufacturers prefer to express the performance of their pump in head, rather than in pressure units, as they can test the pump with a defined liquid (water most of the time), get the head value, and then keep the head value for any further application.

On the other hand, the Process Engineer, when using the performance curve of a pump, must know the liquid density, in order to be able to calculate the actual pressure developped in the system he designs.

## 5. Manufacturers

If you are interested in getting pump characteristics to estimate the head and size of the pump you need for your application, you can contact the pumps GrosClaude : https://www.pompes-grosclaude.com/en/home/

(Note that MyEngineeringTools has no link with this company)

## 6. Free Excel calculation tool to convert head to pressure

You can access an Excel tool to convert head to pressure, and pressure to head, and make the calculations detailed in this page.