Pump Sizing Calculator_Simplified

What this free calculator helps you do

1. estimate hydraulic power
2. calculate shaft power
3. estimate motor input power
4. work with single-stage and multi-stage setups
5. apply series and parallel stage logic
6. calculate NPSH available
7. run quick preliminary pump checks in Excel

A free, single-workbook pump sizing tool from GonokLab for quick preliminary hydraulic and motor sizing of centrifugal (and basic positive-displacement) pumps. Enter your duty point and fluid properties and the workbook returns the power demand at each stage of the drivetrain, plus a suction-side cavitation check.

What it calculates

Sheet 1 — Pump Calculator

• Inputs: pump type, flow rate Q, total head H, fluid density ρ, kinematic viscosity ν, hydraulic / mechanical / motor efficiencies, number of stages, and series/parallel configuration.
• Outputs:
  • Total system head and flow (accounts for series vs. parallel staging)
  • Hydraulic power — useful work delivered to the fluid
  • Shaft power at the coupling — after hydraulic and mechanical losses
  • Motor input (electrical) power — after motor efficiency
  • Shaft power per stage

Sheet 2 — NPSH & Suction

• Inputs: absolute suction pressure, vapor pressure, density, suction pipe velocity, suction head loss, and static elevation (positive when the pump sits above the source).
• Output: NPSH Available using NPSHa = (P_s − P_v) / (ρg) + V²/(2g) − h_fs − z_s, to be compared against the pump's NPSH Required to guard against cavitation.

Worked example shipped with the file

Water at 50 m³/h against 40 m of head, η_h = 75 %, η_mec = 95 %, η_motor = 90 %, single stage: hydraulic power ≈ 5.45 kW, shaft power ≈ 7.65 kW, motor input ≈ 8.50 kW. With 1 bar(a) suction, 0.02 bar(a) vapor pressure, 2 m/s pipe velocity and 1 m friction loss, NPSHa ≈ 9.2 m.

Best for

• Quick preliminary sizing and motor selection
• Students and engineers learning pump hydraulics
• Sanity-checking a vendor selection before requesting formal curves

Limitations

• Simplified model — assumes the user supplies realistic efficiency values rather than deriving them from a pump curve.
• Viscosity is captured as an input but is not used to correct centrifugal pump performance (a note in the file flags this).
• Density is taken as entered — the file reminds users that water is not exactly 1000 kg/m³ at elevated temperature.
• No standard motor-size rounding, no charts, no printable report sheet (those are features of the author's paid editions).

Workbook contents

• Pump Calculator — main duty-point and power calculation
• NPSH & Suction — NPSH available calculation
• Pro Edition Screenshot, Version Comparison, Info — author/marketing material for the paid editions

Author: GonokLab. Free edition; paid Pro and Industrial Premium editions are also offered by the author.