Pump Head Calculator
Total Dynamic Head (TDH) is the total energy, expressed as a height of water, that a pump must add to move fluid at the design flow rate.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the static head (vertical rise from the water source level to the discharge point) in metres. Use a negative value if the source is above the pump (flooded suction).
- Add the friction and fitting losses (from a pipe friction chart or Hazen–Williams / Darcy calculation) and, if the outlet must be pressurised, the required pressure head. Optionally add the discharge velocity for the small velocity-head term.
- Read the Total Dynamic Head (TDH) and equivalent pressure, then match them to a pump performance curve at your target flow rate.
How it works
Total Dynamic Head (TDH) is the total energy, expressed as a height of water, that a pump must add to move fluid at the design flow rate. It is the sum of four parts: static head (the vertical lift), friction head (energy lost to pipe friction and fittings), pressure head (any pressure that must remain at the outlet, converted to metres), and velocity head (the kinetic energy of the moving water). This tool uses TDH = static head + friction losses + pressure head + velocity head.
Velocity head is computed exactly as V² ÷ (2g) with g = 9.80665 m/s², so at 1.5 m/s it is only 0.11 m — usually a minor term. The equivalent pressure is found from the standard relation that a 1 m column of water is about 9.80665 kPa (so 1 bar ≈ 10.2 m). Friction losses depend on pipe diameter, length, roughness and flow, so they are entered as a separate figure rather than assumed; get them from a friction chart or a Darcy/Hazen–Williams calculation for your exact pipe.
Worked example
Sizing a transfer pump for a rainwater tank. A pump lifts water 12 m from a tank to an elevated header tank. Pipe friction plus valves and bends add 3.5 m of loss, and the outlet must deliver 20 m of pressure head; discharge velocity is 1.5 m/s. Entering staticLift = 12, frictionLoss = 3.5, pressureHead = 20 and velocity = 1.5 gives a velocity head of 0.11 m and a Total dynamic head (TDH) of 35.61 m — roughly 349.2 kPa (3.49 bar). You would then pick a pump whose curve delivers your target flow at 35.61 m of head or more.
Common mistakes
- Forgetting friction and fitting losses. Static lift alone under-sizes the pump — long runs, small pipes, valves and elbows can add many metres of head.
- Confusing head with pressure. Head is a height in metres; convert to pressure with 1 m ≈ 9.81 kPa (≈ 0.098 bar), not 1:1.
- Ignoring suction conditions. This tool gives discharge-side TDH; it does not check NPSH (net positive suction head), so a pump can still cavitate even at the right head — verify NPSH separately.
Frequently asked questions
What is Total Dynamic Head (TDH)?
TDH is the total head a pump must overcome at the design flow: the vertical static lift, plus friction and fitting losses, plus any required outlet pressure head, plus the small velocity head. You size a pump by finding the flow it delivers at your TDH on the manufacturer's curve.
How do I get the friction loss figure to enter?
Friction loss depends on pipe diameter, length, material roughness, fittings and flow rate, so it is calculated separately — from a pipe friction chart or a Darcy–Weisbach or Hazen–Williams calculation for your exact system — then entered into the Friction & fitting losses field here.
How do I convert the head result to pressure?
For cold water, 1 metre of head is about 9.81 kPa (0.098 bar), so 1 bar ≈ 10.2 m. This tool shows the equivalent pressure automatically. For hotter water or other fluids the density differs, so adjust accordingly.
Does this size the pump for me?
No. It gives the total dynamic head at your stated flow. You must still match TDH and flow against a real pump performance curve, check NPSH/suction conditions, and confirm the design against local plumbing and building code and a licensed professional.
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