BHP to kW Conversion Calculator

This calculator converts brake horsepower (BHP) to kilowatts (kW) using the standard mechanical horsepower definition. You enter the power in BHP and the calculator returns the equivalent power in kilowatts, along with the result in watts for reference.

Formula

The conversion between brake horsepower and kilowatts is a fixed unit conversion, not a formula that depends on engine speed or torque. The relationship is:

kW = BHP × 0.745699872

Where:

• BHP – brake horsepower, the power measured at the engine’s flywheel (or crankshaft) in imperial horsepower (hp).
• kW – kilowatts, the SI unit of power, equal to 1,000 watts.
• 0.745699872 – the exact conversion factor from one mechanical horsepower to kilowatts.

This factor stems from the definition of mechanical horsepower: 1 hp = 550 foot-pounds per second. When converted to metric units (watts), that equals exactly 745.69987158227022 W, which rounds to 0.745699872 kW.

Worked Example

Using the calculator’s default value of 100 BHP:

1. Start with the power in BHP: 100 hp
2. Multiply by the conversion factor: 100 × 0.745699872 = 74.5699872 kW
3. Round to two decimal places: 74.57 kW

So 100 BHP equals 74.57 kW. The calculator also shows 74,570 W (since 1 kW = 1,000 W).

Why BHP and kW Are Different Units

Brake horsepower is a unit of power used mainly in the UK and some other countries that historically followed British engineering practice. The name comes from the original method of measurement: a brake (dynamometer) applied to the engine’s output shaft to measure its torque and rotational speed. The resulting power is what the engine actually delivers at the flywheel, before losses through the gearbox, driveshaft, and wheels.

Kilowatts are the SI unit of power and are used almost everywhere else in the world, especially in Europe, Australia, and most of Asia. When car manufacturers quote engine output in different markets, they often use the same physical measurement but express it in the local unit. This is why a car might be listed as 150 BHP in the UK and 112 kW in Germany – they represent the same power output.

How to Read the Result

The result tells you the equivalent power in kilowatts. For example:

• 50 BHP → 37.28 kW
• 200 BHP → 149.14 kW
• 500 BHP → 372.85 kW

When comparing vehicles, remember that the number alone doesn’t tell you about acceleration or top speed – those depend on weight, aerodynamics, gearing, and torque curve. But for a direct power comparison, the kW figure is the standard metric measure.

Common Mistakes and Misconceptions

A frequent error is confusing BHP with PS (Pferdestärke, the German metric horsepower). PS is very close to BHP but not identical: 1 PS = 0.73549875 kW, while 1 BHP = 0.745699872 kW. The difference is about 1.4%, so if you use a BHP-to-kW calculator on a PS value, you’ll overstate the power by roughly 1.4%.

Another mistake is mixing up brake horsepower with wheel horsepower (WHP). BHP is measured at the flywheel, while WHP is measured at the wheels after drivetrain losses (typically 10–20% lower). A BHP-to-kW conversion only works if the input is truly BHP, not WHP.

Also, be careful with rounding. The conversion factor has many decimal places, but for most practical purposes, using 0.746 is accurate enough. However, if you need precision for engineering calculations, use the full factor 0.745699872.

When to Use This Conversion

You’ll need this conversion in several situations:

• Comparing engine outputs between vehicles from different markets (UK vs. Europe).
• Reading technical specifications that list power in kW when you’re used to BHP.
• Calculating power-to-weight ratios when one figure is in BHP and the other in kW.
• Estimating electrical power requirements for motors or generators rated in BHP.

For electric motors, BHP is sometimes used to describe mechanical output power. The conversion to kW is the same, but note that the electrical input power will be higher due to motor inefficiency (typically 85–95%).

Limits of the Conversion

This conversion is purely mathematical and has no physical limits – any positive BHP value can be converted. However, the input must be a non-negative number, as negative power doesn’t make sense in this context. The calculator enforces a minimum of 0 BHP.

One limitation is that BHP itself can be measured under different standards (e.g., SAE net, DIN, ECE), which may yield slightly different values for the same engine. These standards define testing conditions and accessory loads, but the conversion factor itself remains the same. If you’re comparing two engines, ensure both BHP figures were measured under the same standard.

Frequently Asked Questions

Is BHP the same as HP?

In most contexts, yes. BHP (brake horsepower) is a specific type of horsepower measured at the engine’s output shaft. The term “HP” alone can be ambiguous, but in automotive specs, it usually refers to the same measurement. There are other types like PS (metric horsepower) and WHP (wheel horsepower), which are different.

How many kW is 1 BHP?

1 BHP equals 0.745699872 kW, or about 0.746 kW. To convert, multiply the BHP figure by this factor. For example, 150 BHP × 0.7457 = 111.85 kW.

Why do some countries use BHP and others use kW?

This is a historical legacy. The UK and some Commonwealth countries adopted imperial units, including horsepower, while most of the world uses the metric system, which includes the kilowatt as the standard power unit. Even after the UK officially adopted metric units, BHP remained common in the automotive industry.

What’s the difference between BHP and PS?

BHP (imperial horsepower) is 745.7 watts, while PS (metric horsepower) is 735.5 watts. The difference is about 1.4%. So 100 BHP is roughly 101.4 PS. When converting, use the correct factor: BHP to kW uses 0.7457, while PS to kW uses 0.7355.

Can I convert kW to BHP with this calculator?

No, this calculator only converts BHP to kW. To go the other way, divide the kW value by 0.745699872. For example, 100 kW ÷ 0.7457 = 134.1 BHP.

Does this conversion work for electric motors?

Yes, the conversion factor is the same regardless of the power source. However, for electric motors, BHP usually refers to the mechanical output power, while the electrical input power is measured in kW and is higher due to losses. Always check which value you’re converting.

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in bhp | Power (BHP) | hp | 100 | 0 | 100000
out kw | Power (kW) | kW | bhp * 0.745699872 | 2
out watts | Power (W) | W | bhp * 745.699872 | 0