How do you calculate motor sizing with this tool?

Multiply all four inputs together: load x operating factor x conversion constant x multiplier. With 100 x 4 x 0.005 x 1 the result is 2 power units.

What is the conversion constant for?

It converts the raw load-times-duty product into your target power unit. The 0.005 in the example collapses flow-and-head style numbers into a manageable power figure — swap it for the constant that matches your unit system.

How do I add a service factor?

Put it in the process multiplier. A 1.0 multiplier gives nameplate sizing; use 1.15 for a common service factor or a higher value to cover startup surge and efficiency losses.

Why is the base product 400 but the result only 2?

The 100 x 4 load and duty product is 400; the 0.005 conversion constant scales that down to 2, and the 1.0 multiplier leaves it unchanged.

Can I use this to pick a final motor?

Use it to narrow the frame size, then verify against the pump curve or compressor thermodynamic power at the actual duty point, plus NEMA/IEC standard ratings and startup torque.

How much margin should I build in?

Many shops target sizing 10-25% above the calculated duty power so the motor is not continuously loaded at 100%; set that with the multiplier rather than oversizing the load inputs.

Pump, Compressor & Rotating Equipment Assembly calculator

Motor Sizing Calculator

Motor Sizing estimates the drive power a pump or compressor needs by chaining the mechanical load, the operating duty factor, a unit-conversion constant and a service or efficiency multiplier. Application and packaging engineers use it as a fast first-pass to pick a motor frame before a full hydraulic or thermodynamic calculation. The conversion constant is what turns raw load-times-duty into engineering power units (for example, flow x head into brake horsepower), and the multiplier lets you add margin for service factor, efficiency or a unit change. It is a sizing sanity check, not a substitute for the pump curve.

What this calculator does

Motor Sizing estimates the drive power a pump or compressor needs by chaining the mechanical load, the operating duty factor, a unit-conversion constant and a service or efficiency multiplier.
Use it when motor sizing in pump, compressor and rotating equipment assembly needs a few factors combined into one defensible number for pump, compressor and rotating equipment assembly.
It multiplies a load factor, an operating factor, a conversion constant and a process multiplier into a single motor-sizing value.

Formula used

Motor Sizing = first factor × second factor × conversion factor × process multiplier
Use the multiplier for unit conversion or process efficiency

Inputs explained

Load flow or torque demand:
Operating factor (head, pressure or duty):
Unit-conversion constant to motor power:
Service factor / efficiency multiplier:

How to use the result

Use it for a quick first-pass motor or drive selection before committing to a detailed hydraulic or compressor power calculation.
It is a linear product and ignores curve shape, part-load efficiency and startup torque, so confirm the final motor against the actual pump or compressor performance curve.

Current U.S. benchmarks

Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.
Manufacturing hourly earnings average $30.27 (BLS, Jun 2026), up 4.4% from a year earlier. Median machinist pay is $28.24/hr (OEWS 2025), with state medians on each state page. Manufacturers have 529k open positions nationally (BLS JOLTS).
Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).
The U.S. has 21,668 machinery manufacturing establishments employing about 1,086,146 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate motor sizing with this tool? Multiply all four inputs together: load x operating factor x conversion constant x multiplier. With 100 x 4 x 0.005 x 1 the result is 2 power units.
What is the conversion constant for? It converts the raw load-times-duty product into your target power unit. The 0.005 in the example collapses flow-and-head style numbers into a manageable power figure — swap it for the constant that matches your unit system.
How do I add a service factor? Put it in the process multiplier. A 1.0 multiplier gives nameplate sizing; use 1.15 for a common service factor or a higher value to cover startup surge and efficiency losses.
Why is the base product 400 but the result only 2? The 100 x 4 load and duty product is 400; the 0.005 conversion constant scales that down to 2, and the 1.0 multiplier leaves it unchanged.
Can I use this to pick a final motor? Use it to narrow the frame size, then verify against the pump curve or compressor thermodynamic power at the actual duty point, plus NEMA/IEC standard ratings and startup torque.

Last reviewed 2026-05-12.