Engineering calculator reviewed for preliminary design use · Last updated: March 2026
Calculate pump total dynamic head (TDH) as the sum of static head, pipe friction losses, and velocity head. Estimate shaft power and motor size accounting for pump efficiency. First step in pump selection and facility design.
What this calculator is used for
Pump head calculation is a fundamental step in selecting pumps for process and
utility systems. A pump must supply enough energy to overcome elevation
difference, piping losses, and required discharge pressure.
Typical engineering use cases
Preliminary pump selection during FEED or basic engineering
Estimating motor power and energy consumption
Evaluating system modifications and their impact on pump duty
Checking adequacy of existing pumps
Governing equation and methodology
Total dynamic head is calculated as the sum of static head, friction losses,
and pressure requirements at the discharge point.
Engineering assumptions and limitations
Single-phase, steady-state flow
Transient effects are not considered
Practical design notes
Design margins are commonly applied to account for fouling and future capacity
increase. Final pump selection should always be verified using manufacturer
performance curves and NPSH calculations.
Worked Example
Given:
Static lift (suction to discharge) = 15 m
Friction + fitting head loss = 8 m
Flow Q = 50 m³/h water (ρ = 998 kg/m³), pump efficiency η = 70 %
Method: TDH = static + friction = 15 + 8 = 23 m (velocity head negligible). Shaft power P = ρ·g·Q·TDH/η = 998·9.81·(50/3600)·23/0.70.
Result: TDH ≈ 23 m; pump shaft power ≈ 4.5 kW.
Interpretation: This is the system duty point, not the pump. You still have to overlay the vendor curve, confirm the operating point sits near the BEP, and verify NPSHa > NPSHr — a 23 m head pump running far right of BEP can cavitate even though the head matches.
Common Mistakes & Misuse
Quoting the calculated TDH as the pump's required power — TDH is a head in metres; shaft power still needs ρgQH/η and the motor needs a further margin above that.
Using gauge discharge pressure as the static head and double-counting it once friction head is added separately.
Sizing on the rated duty point only and ignoring NPSH available vs required, so the pump cavitates at the suction conditions.
Omitting the velocity-head difference between suction and discharge for large diameter changes, where it is no longer negligible.
Treating the system requirement as the selection — the duty must still be intersected with the vendor pump curve, not read off in isolation.
Frequently Asked Questions
What is Total Dynamic Head (TDH)?
TDH is the total equivalent height of fluid that a pump must deliver. It includes static head (elevation difference), friction head (pipe and fitting losses), and velocity head. TDH directly determines the required pump performance.
How is pump shaft power calculated?
Shaft power P = (ρ × g × Q × TDH) / η, where η is the pump efficiency. This gives the mechanical power input to the pump shaft, not the motor electrical power.
Does this replace a pump curve analysis?
No. This tool estimates the system requirement. Final pump selection requires matching the system curve with the vendor pump curve, including NPSH verification and best efficiency point analysis.
For preliminary estimation and educational use only. Results may depend strongly on assumptions, input data, fluid or material properties, and the range of validity of the underlying equation. Verify critical calculations independently and follow the applicable code, specification, and formal engineering review process before using any result for design, procurement, fabrication, operation, or safety decisions.