Unit Conversion: How to Convert Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP)

Unit conversions in electrical engineering are very important; it is relatively easy, but it can also cause many problems when planning or troubleshooting systems.

Horsepower to kilowatts (HP to kW) and kilowatts to horsepower (kW to HP) conversions are very important when the energy and power of internal combustion engines are compared or transferred between energy and power of electric motors, pumps, winches, inverters, and other devices being powered by electric energy.

Updated: September 4, 2024.

Conversion Formulas - How to Convert HP to kW and kW to HP?

Both horsepower (HP) and kilowatt (kW, sometimes written "kilo-watt") are units that measure the power of a system. As a power unit, the 'HP' (Horse Power) has a long history that is beyond the scope of this article (and this site) - it is enough to say that the unit was used to measure the strength of a horse, hence the name, and compare it with the strength of early steam engines.

Today, HP as a unit is mostly used for describing/rating the strength or power of various engines (internal combustion engines, steam turbines, and similar).

On the other hand, 'watt' is an SI unit and is exactly defined.

There are several definitions of HP, including:

Mechanic or hydraulic horsepower (HP): one mechanic or hydraulic horsepower equals 745.699872 W or 0.745699872 kW:

1 HP_I = 745.699872 W = 0.745699872 kW

Electrical horsepower (HP): one electrical horsepower equals exactly 746 W or 0.746 kilowatts:

1 HP_E = 746 W = 0.746 kW

Metric horsepower (HP): one metric horsepower equals 735.49875 W or 0.73549875 kilowatts:

1 HP_M = 735.49875 W = 0.73549875 kW

There are other HP definitions, including tax horsepower, drawbar horsepower, boiler horsepower, etc., but the most used one is electrical horsepower, which defines:

1 HP = 746 W

Since the SI prefix 'kilo' (shortened to 'k') means thousand (or 10³), it also means that:

1 HP = 746 W = 0.746 kW

Likewise:

1 kW = 1/0.746 HP = 1.34048 HP ≈ 1.34 HP

For short:

1 HP = 0.746 kW → P (kW) = 0.746 * P (HP)

1 kW = 1.34 HP → P (HP) = 1.34 * P (kW)

So, if You have value in HPs, multiply it by 0.746 or divide it by 1.34, and You will get the equivalent value in kW (kilowatts) - in most situations, a calculator app on the computer or smartphone can do the job, but sometimes a common calculator can come very handy!

Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP) Conversion Calculator

In order to convert Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP), feel free to use this conversion calculator - write the value that You have and click 'Calculate' to convert it (Note: electric horsepower is assumed):

Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP) Conversion Examples

Here are several HP to kW and kW to HP conversion examples:

0.5 HP to kW: P (kW) = 0.746 * P (HP) = 0.746 * 0.5 = 0.373 kW = 373 W

1 HP to kW: P (kW) = 0.746 * P (HP) = 0.746 * 1 = 0.746 kW = 746 W

5 HP to kW: P (kW) = 0.746 * P (HP)  = 0.746 * 5 = 3.73 kW = 3730 W

50 HP to kW: P (kW) = 0.746 * P (HP) = 0.746 * 50 = 37.3 kW = 37300 W

100 HP to kW: P (kW) = 0.746 * P (HP) = 0.746 * 100 = 74.6 kW = 74600 W

1 kW to HP: P (HP) = 1.34 * P (kW) = 1.34 * 1 = 1.34 HP

1.5 kW to HP: P (HP) = 1.34 * P (kW) = 1.34 * 1.5 = 2.01 HP = ~2 HP

7.5 kW to HP: P (HP) = 1.34 * P (kW) = 1.34 * 7.5 = 10.05 HP = ~ 10 HP

200 kW to HP: P (HP) = 1.34 * P (kW) = 1.34 * 200 = 268 HP = ~270 HP

300 kW to HP: P (HP) = 1.34 * P (kW) = 1.34 * 300 = 402 HP = ~400 HP  

Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP) Conversion Table

The following Horsepower to Kilowatts (HP to kW) and Kilowatts to Horsepower (kW to HP) conversion table lists the power, currents, and voltages of specific loads:

For example, if You want to convert 5 HP to kW, check the chart:

5 HP equals 3.73 kW, or 310.8 Amps @12 volts, 155.4 Amps @24 volts, 103.6 Amps @36 volts, 31.08 Amps @120 volts, and 16.21 Amps @230 volts.

For more examples, feel free to check the Horsepower (HP) to Kilowatts (kW) and Kilowatts (kW) to Horsepower (HP) charts later in this article.

Standard SI Prefixes

SI prefixes are used in order to write down very large or very small numbers - after all, it is much easier to write, for example, 25 kW than 25000 watts. But, it is also much easier to write 25 MW than 25000 kW or 25000000 watts.

The following chart lists the International System of Units (SI) official prefixes:

Note: the 'Short Scale' is in use in, for example, the United States, while the 'Long Scale' is in use in, for example, Europe.

kW to HP and HP to kW Conversion Frequently Asked Questions (FAQ)

Here are some of the most common Frequently Asked Questions (FAQ) about kilowatts to horsepower and horsepower to kilowatts conversion:

Is 1 HP equal to 1 kW? How many kW is equal to 1 HP?

No, 1 HP equals 746 Watts or 0.746 kW - although there are many other definitions for HP, this one is called "Electric Horsepower" and is the most common one and is very similar to "Mechanical Horsepower," which is 745.69987W.

Metric Horsepower, also often labeled as PS (German for "Pferdestärke," horsepower, shorted to PS) equals 735.49875W. Note that there are even more definitions like Boiler Horsepower (9812.5W), Hydraulic Horsepower (745.69987W), Air Horsepower (745.69987), etc.

What is the formula of kW to HP? How many kW is equal to 1 HP?

The formula is 1 kW = 1/0.746 HP = 1.34048257 HP

How many HP is 15 kW?

P(HP) = 15 kW * 1.34 = ~20.1 HP

How do conversions differ for metric horsepower versus imperial horsepower?

The primary difference in converting metric horsepower versus imperial horsepower lies in their definitions and corresponding values.

Metric horsepower, also known as "PS" from the German "Pferdestärke," is defined as exactly 735.5 watts.

Imperial horsepower, commonly used in the United States and referred to as mechanical horsepower, is defined as approximately 745.7 watts.

Therefore, when converting from horsepower to kilowatts, the specific type of horsepower being used must be considered to ensure accuracy, as the conversion factor will vary slightly between the two types. For example:

1 kW = 1000 W → 1000 W / 735.5 PS/W = 1.3596 PS

1 kW = 1000 W → 1000W / 745.7 HPi/W = 1.3410 HPi

Again, in this article, we assume electric horsepower, which is defined as:

1 HP = 746W = 0.746 kW

Long Story Short: Unit conversions, including HP to kW and back, are easy, just be sure to remember the right formulas:

1 HP = 0.746 kW → P (kW) = 0.746 * P (HP)

1 kW = 1.34 HP → P (HP) = 1.34 * P (kW)

And don't forget to use the calculator, especially for larger values. Again, these values are for electric horsepower.