Pump Head Calculator (TDH) ⛽

Total Dynamic Head Formula

• Static head: height from the lowest water level on the suction side to the highest discharge point.
• Friction head: losses in the suction and discharge pipes, valves and fittings at the duty flow.
• Pressure head: the pressure needed at the outlet (for example a fixture, nozzle or tank inlet) less any pressure on the suction tank, plus equipment losses. 10 kPa ≈ 1.02 m of water; 1 psi = 2.31 ft.
• Velocity head: the kinetic energy at the outlet, v²/2g, usually small.

From Head to Pump Power

Hydraulic power P = ρ × g × Q × H; shaft power = hydraulic power ÷ pump efficiency. Choose a motor one standard size above the shaft power, and check the pump's NPSH with the Pump NPSH Calculator. For a quick motor size use the Pump Horsepower Calculator, and for friction in a single pipe the Water Pipe Pressure Drop Calculator.

Tips

• Use the lowest suction level and highest discharge point, not average levels.
• Add 10–15% safety on friction only, not on static head, or the pump will run far right on its curve.
• For booster sets, the outlet pressure is the pressure needed at the highest, most remote fixture.

FAQ

How do you calculate pump head?

Add the static height from the lowest suction level to the highest discharge point, the friction losses in the suction and discharge pipes, and the pressure needed at the outlet converted to head (1 bar ≈ 10.2 m, 1 psi = 2.31 ft).

What is the difference between pump head and pressure?

Head is the height of liquid the pump can lift, independent of density; pressure = density × g × head. For water, 10 m of head is about 98 kPa (1 bar), and 2.31 ft is 1 psi.

How do you convert pump head to kW?

Shaft power in kW = Q (m³/s) × H (m) × 9.81 × density ÷ 1000 ÷ efficiency. For 5 L/s at 45 m and 65% efficiency that is about 3.4 kW.