BHP to kW Conversion Guide

BHP to kW conversion is used when engine or motor power is written in brake horsepower and you need the equivalent value in kilowatts. This appears in car specifications, motorcycle data, marine engines, pumps, generators, industrial motors, compressors, dyno reports, and mechanical engineering calculations. BHP is common in older and regional vehicle specifications, while kW is common in SI-based technical documents and many modern international specifications.

The main conversion is:

So the direct formula is:

If an engine is rated at 100 BHP, then:

Rounded to two decimal places, 100 BHP is 74.57 kW.

What Is BHP?

BHP means brake horsepower. It describes the usable mechanical power measured at an engine or motor output shaft. The word “brake” comes from dynamometer testing, where a braking device or load is used to measure output power. In simple terms, BHP is the power produced by the engine before losses through the gearbox, differential, tires, or other drivetrain parts.

This makes BHP different from wheel horsepower. Wheel horsepower is measured at the wheels after drivetrain losses. If an engine is rated at 200 BHP, the actual power at the wheels may be lower because energy is lost through friction, transmission components, and rotating parts.

What Is a Kilowatt?

A kilowatt is a metric unit of power. One kilowatt equals 1000 watts. A watt is one joule per second:

Kilowatts are widely used in engineering, electric motors, electric vehicles, power stations, generators, HVAC equipment, and international vehicle specifications. Converting BHP to kW helps compare older horsepower-based ratings with metric power ratings.

BHP to kW Formula

The formula for converting brake horsepower to kilowatts is:

Here, \(P_{kW}\) is power in kilowatts and \(P_{BHP}\) is power in brake horsepower. The factor 0.745699872 comes from the mechanical horsepower definition.

For 150 BHP:

Rounded to two decimal places, 150 BHP is 111.85 kW.

kW to BHP Formula

The reverse conversion changes kilowatts back into brake horsepower:

For 100 kW:

Rounded to two decimal places, 100 kW is 134.10 BHP.

BHP to Watts Formula

Because one kilowatt equals 1000 watts, you can also convert BHP to watts directly:

For 10 BHP:

So 10 BHP is approximately 7457 W, or 7.46 kW.

How to Use This Calculator

1. Enter the brake horsepower value.
2. Select how many decimal places you want in the result.
3. Click the conversion button or let the calculator update automatically.
4. Read the kilowatt result.
5. Use the watts value below the result when you need power in watts.

For vehicle comparisons, two decimal places is usually enough. For engineering notes, four or more decimal places may be useful.

Worked Examples

Example 1: Convert 1 BHP to kW

1 BHP is approximately 0.7457 kW.

Example 2: Convert 50 BHP to kW

50 BHP is approximately 37.28 kW.

Example 3: Convert 100 BHP to kW

100 BHP is approximately 74.57 kW.

Example 4: Convert 250 BHP to kW

250 BHP is approximately 186.42 kW.

Example 5: Convert 500 BHP to kW

500 BHP is approximately 372.85 kW.

Common BHP to kW Conversion Table

BHP, HP, PS, and kW

Power ratings can be confusing because several horsepower units exist. BHP usually refers to brake horsepower measured at the shaft. Mechanical horsepower is commonly used in imperial contexts and is approximately 745.7 watts. Metric horsepower, often written as PS, is slightly different and is approximately 735.5 watts. Kilowatts are SI-based and avoid many of these naming differences.

If a specification says horsepower, check whether it means mechanical horsepower, brake horsepower, metric horsepower, or another rating standard. For this calculator, BHP is treated as mechanical brake horsepower using the factor \(0.745699872\text{ kW}\) per BHP.

BHP and Torque

BHP measures power. Torque measures rotational force. They are related, but they are not the same. An engine can produce high torque at low speed or high power at higher speed depending on its design. In imperial units, horsepower can be connected to torque and engine speed with:

Here, \(T\) is torque in pound-feet and \(RPM\) is revolutions per minute. This formula shows that power depends on both torque and rotational speed. A high-torque engine at low RPM may not have the same BHP as an engine that produces less torque but spins much faster.

Where BHP to kW Conversion Is Used

This conversion is useful for comparing car engines, motorcycle engines, boat engines, generators, pumps, industrial motors, compressors, agricultural machines, and performance data from dynamometers. Some manufacturers list power in BHP, while others use kW. Converting to a shared unit makes comparison easier.

For electric vehicles, kW is often the primary power unit. For older vehicle communities, horsepower and BHP are still widely used. If you compare an electric motor rated at 150 kW with an engine rated at 200 BHP, conversion shows that 200 BHP is about 149.14 kW. The two ratings are close in maximum power, though real performance also depends on torque curve, gearing, vehicle weight, traction, and efficiency.

BHP Is Not Always Wheel Power

Brake horsepower is usually measured at the engine or motor output shaft. Wheel horsepower is measured at the wheels after drivetrain losses. These losses can come from the clutch, gearbox, differential, shafts, bearings, tires, and other rotating parts. Because of this, wheel horsepower is usually lower than BHP.

A simple drivetrain efficiency relationship is:

Here, \(\eta\) is drivetrain efficiency as a decimal. If an engine makes 200 BHP and the drivetrain efficiency is 85%, then:

This example is only a simplified estimate. Real drivetrain losses vary by vehicle type, transmission, tire setup, dyno method, and conditions.

Common Mistakes

1. Treating every horsepower label as BHP

Horsepower can mean different things. Mechanical horsepower, brake horsepower, metric horsepower, and wheel horsepower are not always identical.

2. Confusing BHP with torque

BHP is power. Torque is rotational force. A complete performance picture needs both power and torque behavior across RPM.

3. Treating BHP as wheel horsepower

BHP is usually measured before drivetrain losses. Wheel horsepower is measured after drivetrain losses.

4. Forgetting the conversion factor

Use \(1\text{ BHP}=0.745699872\text{ kW}\). Multiplying by 0.7355 would approximate metric horsepower instead, not mechanical BHP.

5. Comparing vehicles by peak power only

Peak power is important, but acceleration and usability also depend on weight, torque curve, gearing, traction, aerodynamics, and power delivery.

Helpful Related Formulas

BHP to watts:

Watts to BHP:

kW to watts:

Watts to kW:

Learning Resources

For more conversion and calculator tools, visit the He Loves Math calculator collection. For unit references, useful public resources include the National Institute of Standards and Technology and the International Bureau of Weights and Measures.

BHP to kW FAQs