kW to HP Converter

Converting between kilowatts and horsepower is vital in engineering for motors, energy systems, and industrial design.
It requires understanding types of horsepower, efficiency, and standards like IEC and NEMA for accurate conversions.

kW to HP Converter

Extensive Conversion Table: Kilowatts to Horsepower (kW to HP)

The following tables present common kilowatt values converted to horsepower, using both metric horsepower (PS) and mechanical horsepower (HP). For clarity:

  • 1 mechanical HP = 745.699872 W
  • 1 metric HP (PS) = 735.49875 W

Table 1: Common kW to HP (Mechanical) Conversion Table

Kilowatts (kW)Horsepower (HP, mechanical)Horsepower (HP, metric)
0.250.3350.340
0.370.4960.503
0.550.7380.748
0.751.0061.020
1.11.4751.496
1.52.0122.040
2.22.9512.993
3.04.0224.078
4.05.3645.437
5.57.3767.500
7.510.05910.170
11.014.74914.782
15.020.11720.340
18.524.81625.167
22.029.51529.994
30.040.23540.680
37.049.67550.171
45.060.35261.020
55.073.81274.460
75.0100.587101.700
90.0120.704122.040
110.0147.190149.820
132.0176.583179.520
160.0214.688217.920
200.0268.360272.160
250.0335.450340.200
315.0422.358428.580

Note: Always verify whether you’re using mechanical (US) or metric (EU/Asia) HP for your application.

Key Formulas for kW to HP Conversion

There are three main conversion formulas used depending on the type of horsepower you’re working with. These distinctions are crucial for ensuring accurate motor sizing or power rating in engineering contexts.

Formula 1: kW to Mechanical Horsepower (Imperial)

Where:

Example:

Formula 2: kW to Metric Horsepower (PS)

Where:

  • 735.49875 = Watts per metric horsepower (PS, used in EU/Asia)

Example:

Formula 3: HP to kW Conversion

For reverse conversion:

  • Mechanical HP:
  • Metric HP:

Explanation of Variables and Typical Values

These constants are based on international metrology standards (see NIST reference).

Real-World Applications: Case Studies

Case Study 1: Industrial Motor Selection

Scenario:
An industrial facility in the U.S. is upgrading a conveyor system. The design requires a 22 kW motor, and the engineering team must ensure compatibility with the installed drives which are rated in HP.

Steps:

1.Convert 22 kW to HP (mechanical):

    2.Round to standard motor sizes:
    NEMA standard sizes include 30 HP motors, so a 30 HP motor would be chosen.

    3.Check current draw:
    Use the formula:

      Result: 30 HP, 400V motor selected with 40 A full-load current.

      Case Study 2: Electric Vehicle Motor Comparison

      Scenario:
      An engineer compares two EV motors—one rated at 75 kW and another at 100 HP—for torque analysis.

      Steps:

      1.Convert 100 HP (mechanical) to kW:

      2.Compare Outputs:

      • Motor A: 75 kW
      • Motor B: 74.57 kW (100 HP)

      3.Conclusion:
      Power difference is negligible. Engineer chooses based on torque curve and weight efficiency.

        Result: Conversion helped standardize comparison across metric and imperial units.

        Factors That Influence Conversion Accuracy

        While the formulas are fixed, real-world implementations vary depending on:

        • Efficiency losses (e.g., motor ≠ 100% efficient)
        • Voltage fluctuations
        • Load types (inductive vs resistive)
        • Ambient temperature and derating

        Always validate nominal ratings with actual performance under load.

        When to Use Mechanical vs Metric Horsepower

        Use CaseRecommended Unit
        U.S. Industrial EquipmentMechanical HP
        EU/Asia SpecificationsMetric HP (PS)
        Automotive (International)Usually Metric HP
        Engineering SimulationsTypically use kW

        Regulatory and Engineering Standards

        • IEC 60034 – Rotating electrical machines (kW as standard).
        • NEMA MG1 – U.S. motors (HP used).
        • ISO 1000 – SI units including kW.

        More info:

        Frequently Asked Questions (FAQ)

        Is there a difference between electric and mechanical HP?

        Yes. Electric HP (used in motors) is often rounded to 746 W, but true mechanical HP is defined as 745.699872 W. For precision, always use full value unless manufacturer uses nominal 746 W.

        Why do some automotive systems report HP differently?

        European vehicles use PS (Pferdestärke) which equals 735.49875 W. In North America, SAE-certified mechanical HP is standard.

        Is the conversion reversible?

        Yes. Conversions are symmetrical. However, due to rounding, reverse conversions may yield slightly different results (e.g., 75 kW → 100.587 HP → 75.01 kW). Use consistent precision.

        Summary Table: All Conversions and Constants at a Glance

        MetricValue
        1 HP (mechanical)745.699872 W
        1 HP (metric, PS)735.49875 W
        1 kW to HP (mechanical)1.341
        1 kW to HP (metric)1.360
        1 HP to kW (mechanical)0.7457
        1 HP to kW (metric)0.7355