Motor Horsepower Calculator
Convert motor ratings between kilowatts and horsepower, including input power.
About Motor Horsepower Calculator
Mechanical and metric horsepower differ by about 1.4 per cent, which matters when comparing specifications from different markets. Motor ratings always refer to shaft output. Quoting input power as though it were the rating overstates a motor by its efficiency, which is how undersized machines get specified.
Formula
Motor Horsepower
1 hp = 745.7 W mechanical; 1 metric hp (PS) = 735.5 W
- hp
- Mechanical or imperial horsepower
- PS
- Metric horsepower, slightly smaller
Worked example
With the default values below, Motor Horsepower Calculator returns Mechanical Horsepower of 20.1153. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Motor ratingminimum 0 kW
- 15 kW
- Motor efficiencyaccepts 0–100 %
- 91 %
- Rated speedminimum 1 rpm
- 1,455 rpm
Results
- Mechanical Horsepower
- 20.1153 hp
- Metric Horsepower
- 20.3943 PS
- Electrical Input Power
- 16.4835 kW
- Torque at Rated Speed
- 98.446 N m
- Input Power in Horsepower
- 22.1048 hp
Step by step
- 1Values used
- 2Motor Horsepower
- 3Mechanical Horsepower= 20.1153 hp
- 4Metric Horsepower= 20.3943 PS
- 5Electrical Input Power= 16.4835 kW
- 6Torque at Rated Speed= 98.446 N m
- 7Input Power in Horsepower= 22.1048 hp
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Motor Horsepower calculated?
1 hp = 745.7 W mechanical; 1 metric hp (PS) = 735.5 W Mechanical and metric horsepower differ by about 1.4 per cent, which matters when comparing specifications from different markets. Motor ratings always refer to shaft output.
Why does Motor Horsepower matter?
Quoting input power as though it were the rating overstates a motor by its efficiency, which is how undersized machines get specified.
What values do I need to enter?
This calculator takes 3 inputs: Motor rating, Motor efficiency, Rated speed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.