Motor HP to kW Calculator
Quickly convert electric motor horsepower (HP) to kilowatts (kW) for motor sizing, electrical drawings, equipment selection, and industrial engineering applications.
Motor HP to kW Calculator
How to Use Motor HP to kW Calculator
Converting electric motor power ratings from horsepower (HP) to kilowatts (kW) is an essential task for industrial electrical engineering, power distribution design, and machinery configuration. Knowing the exact kilowatt rating helps size overload circuit breakers, supply branch wiring, and configure variable frequency drives (VFDs). Follow these step-by-step instructions to convert your motor power rating:
- 1Enter horsepower value. Input the rated nominal motor horsepower value as listed on the motor's metal rating nameplate.
- 2Choose horsepower standard. Select either Mechanical Horsepower (HP) for US/UK machinery or Metric Horsepower (PS) for European standards from the dropdown list.
- 3Click calculate. Press the Calculate button to run the conversion model.
- 4Review converted kilowatts. The primary results box will instantly display the output in kilowatts (kW), along with details about the exact conversion factor and formula used.
- 5Use result for engineering calculations. Apply this active power value to calculate full-load current, motor line current, or system distribution capacity.
This streamlined process helps avoid human sizing errors when installing machinery from global manufacturers. To check the reverse calculation, you can also use our motor kW to HP calculator.
How to Calculate Motor HP to kW
Converting horsepower to kilowatts relies on standardized conversion ratios that define the relationship between imperial units of work, metric mechanical standards, and the metric SI unit for power (watts). Here are the standard formulas and step-by-step engineering instructions:
Formula 1 — Mechanical Horsepower to kW
Mechanical horsepower (also known as imperial horsepower) is defined as 550 foot-pounds per second. It equates to exactly 745.699872 watts. To convert mechanical horsepower to kilowatts, multiply the horsepower by the conversion constant:
Formula 2 — Metric Horsepower to kW
Metric horsepower (Pferdestärke, abbreviated as PS) is defined as the power required to raise a 75-kilogram weight vertically by 1 meter in 1 second. It equates to exactly 735.49875 watts. To convert metric horsepower to kilowatts, multiply the PS value by the conversion constant:
Step-by-Step Engineering Worked Examples
Example 1 — 10 Mechanical HP Motor
Convert a standard 10 HP NEMA industrial electric motor to kilowatts:
Rounding to a standard rating, a 10 HP motor equates to 7.46 kW.
Example 2 — 20 Metric HP Motor
Convert a European-built pump motor rated at 20 PS (metric horsepower) to kilowatts:
Rounding to standard operating parameters, a 20 PS motor equates to 14.71 kW.
Applications in Electrical Engineering
In electrical engineering and motor selection, active power (kW) is the critical parameter for evaluating the electrical loads of an installation. Converting horsepower to kilowatts allows you to calculate the electrical active input power (after applying the motor efficiency) and subsequently size branch conductors, thermal protection relays, and circuit breakers. If you need to estimate starting current reduction ratios or configure terminal links, check our star-delta motor current calculator or find overall details using the motor nameplate calculator.
Motor HP to kW Chart
This conversion chart lists common industrial motor horsepower ratings from 1 HP up to 500 HP and displays their exact converted kilowatt (kW) values. Both Mechanical HP and Metric HP (PS) standards are provided. For choosing matching enclosures, refer to the motor sizing calculator.
| Horsepower | Mechanical HP (kW) | Metric HP (kW) |
|---|---|---|
| 1 HP | 0.746 kW | 0.735 kW |
| 2 HP | 1.491 kW | 1.471 kW |
| 3 HP | 2.237 kW | 2.206 kW |
| 5 HP | 3.729 kW | 3.677 kW |
| 7.5 HP | 5.593 kW | 5.516 kW |
| 10 HP | 7.457 kW | 7.355 kW |
| 15 HP | 11.185 kW | 11.032 kW |
| 20 HP | 14.914 kW | 14.710 kW |
| 25 HP | 18.642 kW | 18.388 kW |
| 30 HP | 22.371 kW | 22.065 kW |
| 40 HP | 29.828 kW | 29.420 kW |
| 50 HP | 37.285 kW | 36.775 kW |
| 75 HP | 55.927 kW | 55.162 kW |
| 100 HP | 74.570 kW | 73.550 kW |
| 125 HP | 93.212 kW | 91.937 kW |
| 150 HP | 111.855 kW | 110.325 kW |
| 200 HP | 149.140 kW | 147.100 kW |
| 250 HP | 186.425 kW | 183.875 kW |
| 300 HP | 223.710 kW | 220.650 kW |
| 400 HP | 298.280 kW | 294.200 kW |
| 500 HP | 372.850 kW | 367.749 kW |
Note: All table values are rounded to three decimal places. In industrial and commercial applications, round the calculated kW rating to the nearest standard manufacturer power rating for compliance.
Unit Standardization: SI vs. Imperial Sizing in Motor HP to kW
When working with Motor HP to kW calculations, using consistent physical units is vital. Small translation errors between SI Metric units (like millimeters, kilowatts, and meters) and Imperial units (like AWG wire, horsepower, and feet) can lead to serious sizing errors:
| Dimension | SI Metric Unit | Imperial Unit | Conversion Conversion Factor |
|---|---|---|---|
| Power | Kilowatts (kW) | Horsepower (HP) | 1 kW ≈ 1.341 HP |
| Length | Meters (m) | Feet (ft) | 1 m ≈ 3.2808 ft |
| Flow Rate | Cubic meters/hr (m³/h) | Gallons/minute (GPM) | 1 m³/h ≈ 4.403 GPM |
Always perform unit checks before installing physical components for Motor HP to kW to ensure they match equipment specification sheets.
Motor HP to kW Frequently Asked Questions
One mechanical horsepower (HP) is equal to 0.745699872 kilowatts (kW). One metric horsepower (PS) is equal to 0.73549875 kilowatts (kW). In general industrial applications, engineers use the approximate value of 1 HP = 0.746 kW for standard three-phase AC induction motors.
No, motor horsepower is not uniform globally. The United States and United Kingdom primarily use mechanical horsepower (imperial HP, ~745.7 W). Continental Europe uses metric horsepower (PS or Pferdestärke, ~735.5 W). This minor difference is critical when designing electrical drives and matching imported machinery.
HP (Horsepower) is an imperial unit of power defined by mechanical work (550 ft-lbs/sec), whereas kW (Kilowatt) is the metric SI unit representing active power flow (1000 Joules/sec). While HP is common in North American NEMA specifications, kW is the international standard defined by the IEC.
Converting motor HP to kW is essential for electrical engineering calculations such as sizing power cables, selecting overload relays, calculating full-load amps (FLA), and designing branch circuits, because active power (kW) is the standard input parameter for electrical systems.
Metric horsepower, abbreviated as PS (from German Pferdestärke), is defined as the power required to lift a 75-kilogram mass vertically by 1 meter in 1 second, equivalent to 735.49875 watts. It is commonly used by European manufacturers for automotive and motor power specifications.
Mechanical horsepower, or imperial horsepower (HP), is a unit of power originally defined by James Watt and standardized as 550 foot-pounds of work per second. This is equivalent to 745.699872 watts, and it remains the primary power unit for industrial motors in NEMA markets.
You should select the standard based on your equipment's country of origin. If you are working with American or British equipment, choose Mechanical HP (US). If you are working with European machinery (IEC standards, DIN standards), select Metric HP (PS) to ensure calculation accuracy.
Yes, the conversion factors are mathematically exact definitions. 1 mechanical HP is exactly 745.699872 watts, and 1 metric HP (PS) is exactly 735.49875 watts. However, nameplate ratings are often rounded by manufacturers to standard frame sizes, so minor discrepancies may exist in real-world equipment.