CalcPanel

Pump Sizing Calculator

Get total dynamic head and shaft power from the pipe, or from a head you already know.

Pump and pipe inputs

What do you need?
Enter upward lift as a positive number. Flooded suction is not modeled.
Visible default for the selected material. Edit it when the pipe is worn or lined.
Default 70%. Allowed range is above 0% through 100%.
Advanced settings
0 to 100 °C fills density and viscosity from a planning table. Leave blank to keep the 20 °C round defaults.

Fitting counts use K v² / (2 g). Default K values are planning assumptions, not a fitting catalog.

About this calculator

One task: required flow, total dynamic head, and shaft power for a single liquid line. It does not use electrical power factor. Browse the power calculators hub for motor power and plant load tools.

Result

Total dynamic head 46.45 ft (14.16 m)

Static head 35.00 ft. Pressure head 0. Pipe friction 11.45 ft. Fitting loss 0. Hydraulic power 0.437 kW. Shaft power 0.624 kW at 70% efficiency.

Planning estimate. Confirm the pump with the manufacturer curve and applicable standards.

Assumptions: water near 20°C, density 998 kg/m³, viscosity 0.001 Pa·s, PVC roughness 0.0015 mm, and 70% pump efficiency. Results are estimates based on the inputs and assumptions provided. Actual pump and piping system performance may vary with equipment characteristics, installation conditions, fluid properties, and manufacturer data.

Continue Your Calculation

Open the same flow and pipe in the pressure-drop calculator to see velocity, Reynolds number, and friction factor.

Pipe pressure drop →

Default roughness and fitting K

InputDefaultMeaning
PVC / copper0.0015 mmSmooth thermoplastic or drawn tube
HDPE0.007 mmConservative plastic roughness
Steel / stainless / cast iron0.045 / 0.015 / 0.26 mmNew commercial pipe, planning values
Elbow / valve / tee / entrance / exitK = 0.9 / 0.2 / 0.6 / 0.5 / 1.0Standard elbow, open gate valve, line-flow tee, sharp inlet, pipe exit

These defaults are shown in the form and can be edited. They are engineering assumptions, not a manufacturer database.

Feet and meters of water to psi

Water at 20°C, density 998.21 kg/m³, the same value the calculator uses. 1 ft is 0.4328 psi, shown below as 0.433 psi. 300 ft × 0.4328 = 129.8 psi. 1 m = 1.42 psi. Hot water and glycol are not on this chart.

HeadPressure
1 ft0.433 psi
10 ft4.33 psi
100 ft43.3 psi
300 ft129.8 psi
1 m1.42 psi

Formula

Total dynamic head = static head + pressure head + pipe friction + fitting loss. The same path applies to a water pump, including a chilled-water or condenser-water line. It does not size HVAC airflow.

Pipe friction uses Darcy-Weisbach: hf = f L v² / (2 g D). Laminar flow (Re < 2300) uses f = 64 / Re. Turbulent flow uses the Haaland 1983 explicit Colebrook approximation. Fitting loss is hf = K v² / (2 g). Pressure head is P / (ρ g). Hydraulic power is ρ g Q H. Shaft power is hydraulic power / efficiency.

The chain is flow, velocity, Reynolds number, friction factor, head loss, then shaft power. This is a hydraulic result, not an electrical power-factor calculation. After you have shaft power, convert it with the HP to kW calculator or screen motor current with motor FLA.

Worked example

50 GPM, 35 ft static lift, 250 ft of 2 in PVC (roughness 0.0015 mm), no discharge pressure, no fittings, 70% efficiency, water at about 20°C.

The calculation engine returns velocity 1.56 m/s, Reynolds number 78,906, friction factor 0.0188, turbulent flow, pipe friction 11.45 ft, fitting loss 0, and total dynamic head 46.45 ft (14.16 m). Hydraulic power is 0.437 kW (0.586 hp). Shaft power is 0.624 kW (0.837 hp). Use the pipe pressure drop link if you want that friction restated in psi.

Known-head screen, friction not included: 300 ft at 10 GPM, 70% efficiency, 20°C water gives 1.08 hp shaft power (0.807 kW). The same head at 5 GPM is 0.54 hp. A long borewell drop pipe adds friction, so enter the pipe before selecting a motor.

FAQ

What is total dynamic head?

Total dynamic head is static lift plus discharge pressure head plus straight-pipe friction plus fitting loss. This page shows each part in feet and meters.

How is pipe friction calculated?

Friction uses the Darcy-Weisbach equation. Laminar flow uses f = 64/Re. Turbulent flow uses the Haaland approximation of Colebrook-White. The result lists Reynolds number and the friction factor.

Does this calculator select a pump model?

No. It estimates required flow, total dynamic head, and shaft power. It does not compare manufacturer curves, NPSH, or catalog model numbers.

Why is shaft power higher than hydraulic power?

Hydraulic power is density times gravity times flow times head. Shaft power divides that by pump efficiency, so a 70 percent efficient pump needs more input power than the water gains.

What if I already know the total head?

Choose Shaft power from a known total head. Enter flow, that head, and efficiency. The page does not add pipe friction again. Switch back to the pipe path when the head still needs to be built.

How do I calculate the head of a pump?

Add static lift, discharge pressure head, straight-pipe friction, and fitting loss. Friction uses Darcy-Weisbach. If you already know the total head, use Shaft power from a known total head so friction is not added twice.

How do I convert feet of head to PSI?

For water at 20°C (998.21 kg/m³, the density this calculator uses), 1 ft of head is 0.433 psi and 1 m is 1.42 psi. The same factor converts TDH in feet to psi. A tank's head is the vertical water height above the outlet: 10 ft is 4.33 psi.

How much HP is required for 300 feet of head?

Head alone does not set horsepower. At 10 GPM, 300 ft entered as known head, 70% pump efficiency, and 20°C water, shaft power is 1.08 hp (0.807 kW). At 5 GPM the same head is 0.54 hp. Pipe friction is not included; add the pipe when the drop pipe is long. Shaft power is not yet motor input; convert it with the HP to kW calculator.