Horsepower to Kilowatts: Equation & Converter

This calculator converts horsepower to kilowatts (kW) and kilowatts to horsepower. Enter a value in either unit, and you get the equivalent in the other unit instantly. The conversion is a simple multiplication: 1 horsepower (mechanical) equals 0.7457 kilowatts.

Formula

The equation for converting mechanical horsepower to kilowatts is:

kW = hp × 0.7457

To convert kilowatts to horsepower, use:

hp = kW ÷ 0.7457

Where:

• hp = power in mechanical horsepower (the unit commonly used for car engines, lawn mowers, and industrial motors)
• kW = power in kilowatts (the SI unit of power, used in electrical engineering and most of the world)
• 0.7457 = the exact conversion factor (1 hp = 745.7 watts = 0.7457 kW)

Worked Example

Using the default value of 100 horsepower:

1. Start with the formula: kW = hp × 0.7457
2. Plug in 100 hp: kW = 100 × 0.7457
3. Multiply: kW = 74.57

The calculator shows 74.57 kW, which matches. So a 100 hp engine produces about 74.6 kilowatts of mechanical power.

Why Are There Different Horsepower Units?

Horsepower is not a single, universal unit. The most common is mechanical horsepower (also called imperial horsepower), defined as exactly 745.7 watts. However, you may encounter others:

• Metric horsepower (PS or CV): used in Europe and Japan, equals 735.5 watts. To convert metric hp to kW, multiply by 0.7355.
• Electrical horsepower: used for electric motors, equals exactly 746 watts. To convert, multiply by 0.746.
• Boiler horsepower: a historical unit for steam boilers, equals about 9.81 kW. Rarely used today.

When someone says “horsepower” without qualification, they almost always mean mechanical horsepower. But if you are working with European car specs or electric motors, check which variant is being used to avoid a 1.4% error.

How to Read the Result

The result tells you the equivalent power in kilowatts. For example, a 200 hp car engine produces about 149 kW. This is useful when comparing vehicles from different countries (US uses hp, most others use kW) or when sizing electrical equipment. A kilowatt is 1,000 watts, so 74.57 kW is 74,570 watts. For reference, a typical household microwave uses about 1 kW, so a 100 hp engine could power roughly 74 microwaves simultaneously (in theory, ignoring losses).

Common Mistakes and Misconceptions

One frequent error is mixing up mechanical and metric horsepower. If you convert 100 metric PS using the mechanical factor, you get 74.57 kW, but the correct answer is 73.55 kW – a difference of about 1.4%. Another mistake is forgetting that kW is already a multiple of watts; do not multiply by 1,000 again. Also, when converting kilowatts to horsepower, some people divide by 0.7457 but then round too early. For example, 150 kW ÷ 0.7457 = 201.15 hp, not 200 hp. Always keep at least three significant figures during intermediate steps.

Limits of the Formula

This conversion is purely mathematical – it changes units, not the physical quantity. It works for any power value, whether from an engine, motor, or generator. However, it does not account for real-world efficiency losses. A car engine’s horsepower is measured at the crankshaft (brake horsepower), but the power actually reaching the wheels is lower due to drivetrain losses. Similarly, an electric motor’s input electrical power (kW) is higher than its output mechanical power (hp) because of heat and friction. The conversion tells you the equivalent power, not the usable power.

When to Use This Conversion

You might need this conversion when:

• Comparing car specifications from different countries (e.g., a European car listed in kW vs. a US car in hp)
• Sizing a generator or inverter for an appliance that lists power in hp
• Converting motor ratings for industrial equipment (many motors list both hp and kW)
• Understanding electricity bills – your utility charges per kWh, so knowing kW helps estimate operating cost

Frequently Asked Questions

How many kilowatts in 1 horsepower?

One mechanical horsepower equals 0.7457 kilowatts. That is the standard conversion factor. For metric horsepower, it is 0.7355 kW.

How do I convert kW to hp?

Divide the kilowatt value by 0.7457. For example, 50 kW ÷ 0.7457 = 67.05 hp. If you are converting to metric horsepower, divide by 0.7355.

Is horsepower the same as kilowatts?

No, they are different units measuring the same thing: power. Horsepower is an imperial unit, kilowatts is the SI unit. One hp is about three-quarters of a kW.

Why do car engines use horsepower instead of kilowatts?

Horsepower is a historical unit that became popular in the 18th century when James Watt used it to market steam engines. Many countries, especially the US and UK, kept using it for vehicles. Most other countries use kilowatts for official specs, but some still quote horsepower informally.

What is the difference between brake horsepower and horsepower?

Brake horsepower (bhp) is the power measured at the engine’s output shaft, before any transmission losses. It is essentially the same as mechanical horsepower. The term “brake” comes from the dynamometer (brake) used to measure it. In practice, bhp and hp are used interchangeably for engine output.

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in hp | Horsepower (mechanical) | hp | 100 | 0
out kw | Kilowatts | kW | hp * 0.7457 | 2