Calculate Total Dynamic Head (TDH) for pump selection and sizing
Mechanical Calculator
Pump head & power — Quick answer
Pump head is the total energy per unit weight a pump must add to move fluid (static lift + friction + velocity + pressure). Hydraulic power follows from head × flow.
Worked example: Water pump, Q = 50 L/s = 0.05 m³/s, total head H = 20 m, efficiency 70%. Phyd = 1,000 × 9.81 × 0.05 × 20 = 9,810 W = 9.81 kW. Pshaft = 9.81 / 0.70 = 14.0 kW. Select 15 kW motor.
Pump power vs flow / head (water, 70% efficiency)
Flow (L/s)
H = 10 m
H = 20 m
H = 50 m
H = 100 m
10
1.4 kW
2.8 kW
7.0 kW
14.0 kW
25
3.5 kW
7.0 kW
17.5 kW
35.0 kW
50
7.0 kW
14.0 kW
35.0 kW
70.0 kW
100
14.0 kW
28.0 kW
70.0 kW
140 kW
250
35.0 kW
70.0 kW
175 kW
350 kW
Standard / source: Hydraulic Institute Standards (HI); ANSI/HI 1.3 (centrifugal pumps); ISO 9906 (pump performance testing).
Used for: Centrifugal pump selection, motor sizing for water/wastewater pumping, chiller-loop circulator pumps, irrigation design, fire-protection pump sizing.
🚿 Pump Head Calculator
Formula
This calculator uses the standard pump head calculator formula:
TDH Formula
TDH = Static Head + Friction Head + Velocity Head + Pressure Head Pressure Head = (P2 − P1) / (ρ · g) [Pa, kg/m³, m/s²]
Frequently Asked Questions
What is Total Dynamic Head (TDH)?⌄
TDH is the total equivalent height a pump must work against. It includes static head (elevation), friction losses in pipes, and velocity head: TDH = Static Head + Friction Head + Velocity Head.
What is static head in a pump system?⌄
Static head is the vertical distance between the pump inlet and the highest discharge point. It represents the minimum energy the pump must provide to lift the fluid.
How do I calculate friction head loss?⌄
Friction head = (f × L × v²) / (D × 2g), where f = Darcy friction factor, L = pipe length (m), v = velocity (m/s), D = pipe diameter (m), g = 9.81 m/s².
What is velocity head?⌄
Velocity head = v² / (2g). It represents the kinetic energy of the fluid at the outlet expressed as an equivalent head. For most systems it is small compared to static and friction head.
Why is TDH important for pump selection?⌄
TDH determines the pump's duty point on its performance curve. Selecting a pump with insufficient head results in under-delivery; too much head wastes energy.
What units is pump head measured in?⌄
Pump head is measured in metres (m) of fluid or feet (ft) in US customary units. Pressure can be converted: 1 bar ≈ 10.2 m of water head.
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Total dynamic head = static lift + friction losses + minor (fitting) losses. Darcy–Weisbach with the Colebrook–White friction factor is the general method; Hazen–Williams is a water-only empirical alternative.
NPSH available must exceed NPSH required, or the pump cavitates and destroys its impeller — a check this calculator does not perform. Also: minor losses through fittings can exceed the straight-pipe friction on a short, fitting-heavy run.
Independently verified
12 July 2026 — Re-derived from the governing standard and checked numerically against worked reference cases from the standard itself — not merely tested for “returns a number”.
Results are for guidance. Verify against the current edition of the governing standard and have a qualified professional review before use in practice.