Kilowatts to Horsepower: Calculator & Formula

This calculator converts power in kilowatts (kW) to mechanical horsepower (hp) instantly. Enter the power value in kilowatts, and you get the equivalent in horsepower, along with the conversion factor used. The standard conversion is 1 kW = 1.34102 hp (mechanical).

Formula

The conversion between kilowatts and horsepower depends on which definition of horsepower you use. The most common in the United States is mechanical horsepower (hp), defined as exactly 745.69987158227022 watts. To convert:

hp = kW × 1.34102

Where:

• hp = mechanical horsepower (unit: hp)
• kW = power in kilowatts (unit: kW)
• 1.34102 = conversion factor (derived from 745.7 W per hp)

For metric horsepower (PS or cv), the factor is different: 1 kW = 1.35962 PS. This is because metric horsepower is defined as 735.49875 watts.

Worked Example

Using the default value of 100 kW:

1. Start with the formula: hp = kW × 1.34102
2. Plug in 100 kW: hp = 100 × 1.34102
3. Multiply: hp = 134.102
4. Round to two decimals: 134.10 hp

The calculator also shows metric horsepower: 100 kW × 1.35962 = 135.96 PS.

Why Two Horsepower Definitions?

Horsepower was coined by James Watt in the 18th century to compare steam engines to draft horses. He measured that a horse could lift 550 pounds one foot in one second, giving 550 ft·lbf/s = 745.7 W. That became the mechanical horsepower used in the US and UK.

Continental Europe adopted a slightly different value based on the metric system: 75 kgf·m/s = 735.5 W. This is called metric horsepower (PS, cv, or ch). When you see a European car’s power in “PS,” it’s not the same as US hp.

For most practical purposes, the difference is about 1.4%—small but noticeable when comparing specs across regions.

How to Choose the Right Conversion

Which factor you use depends on context:

• US/UK vehicles and machinery: use mechanical hp (1 kW = 1.34102 hp)
• European cars and motorcycles: use metric hp (1 kW = 1.35962 PS)
• Electric motors: often rated in kW; if you need hp for motor sizing, use mechanical hp unless the motor is built to IEC standards, then metric.
• Boiler horsepower: a rare unit (1 boiler hp = 9.81 kW) used for steam boilers—don’t confuse it.

When in doubt, ask which standard the spec uses. Many international datasheets list both.

Common Mistakes and Misconceptions

A frequent error is using the wrong factor. For example, converting 100 kW to metric hp gives 135.96, but to mechanical hp gives 134.10—a 1.86 hp difference. Another mistake is rounding too early. If you round the conversion factor to 1.34, you get 134 hp instead of 134.10—a small error that can matter in engineering.

Another misconception: some people think “horsepower” is a measure of speed. It’s a measure of power—the rate of doing work. A high-horsepower engine can accelerate quickly, but top speed also depends on aerodynamics, gearing, and weight.

Also, don’t confuse kilowatts (power) with kilowatt-hours (energy). A 100 kW motor running for 1 hour consumes 100 kWh of energy.

Real-World Examples

Here are some typical conversions to give you a sense of scale:

• A 75 kW electric car motor → 75 × 1.34102 = 100.58 hp (about 100 hp)
• A 150 kW tractor → 150 × 1.34102 = 201.15 hp
• A 2 kW shop vacuum → 2 × 1.34102 = 2.68 hp (but often labeled as “peak hp” which is marketing)
• A 500 kW industrial generator → 500 × 1.34102 = 670.51 hp

Notice how the numbers scale linearly—double the kW, double the hp.

Limits of the Formula

The conversion is exact for mechanical horsepower because the definition is fixed. However, real-world power measurements can vary due to:

• Measurement conditions: SAE net vs. gross, DIN, or JIS standards give different numbers for the same engine.
• Drivetrain losses: wheel horsepower is lower than engine horsepower.
• Electric vs. combustion: electric motors produce full torque at zero RPM, so their power curves differ, but the unit conversion remains the same.

Always check which standard the original number uses. The formula itself never changes, but the input might already be inflated or deflated by the testing method.

Frequently Asked Questions

How many horsepower is 1 kilowatt?
1 kW is equal to 1.34102 mechanical horsepower, or 1.35962 metric horsepower. The first is used in the US/UK, the second in Europe.

What is the difference between hp and PS?
HP (mechanical) and PS (metric) are both horsepower, but they use different definitions. PS is about 1.4% smaller than hp. For example, 100 PS = 98.6 hp.

Why do electric motors list power in kW instead of hp?
Because the SI unit for power is the watt, and kilowatts are a convenient multiple. Many countries use kW for all machines, including cars, to avoid the ambiguity of horsepower definitions.

Can I convert kW to horsepower for a car’s engine?
Yes, if the car’s power is given in kW, multiply by 1.34102 to get mechanical hp. But be aware that European cars often list PS, which is metric hp—use 1.35962 instead.

Is a 100 kW motor the same as a 134 hp motor?
Yes, approximately. 100 kW equals 134.10 mechanical hp. If the motor is rated in metric hp, it would be 135.96 PS.

What about electrical horsepower?
There’s also an “electric horsepower” used historically: 1 electric hp = 746 W exactly. This is slightly different from mechanical hp (745.7 W). It’s rarely used today, but you might see it in old electrical engineering texts.

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in kw | Power | kW | 100 | 0
out hp | Horsepower (mechanical) | hp | kw * 1.34102 | 2
out hp_metric | Horsepower (metric) | hp(M) | kw * 1.35962 | 2