kW to HP Calculator
Convert kW to mechanical, electrical, or metric horsepower. Live calculator with exact constants and worked examples for motor sizing.
Common conversions
| Input | Result |
|---|---|
| 1 kW | 1.34 HP |
| 2 kW | 2.68 HP |
| 5 kW | 6.71 HP |
| 7.5 kW | 10.06 HP |
| 10 kW | 13.41 HP |
| 37 kW | 49.62 HP |
| 75 kW | 100.58 HP |
| 150 kW | 201.15 HP |
The math behind it
- HP = 18.5 / 0.7457
- HP = 24.809...
- HP ≈ 24.81 HP
Everything you need to know
Mechanical horsepower equals 745.7 watts, or 0.7457 kW. It's the constant printed in NEC tables and used on most North American motor nameplates. Two related units cover the rest of the world's data sheets: electrical horsepower, fixed at exactly 746 W, and metric horsepower (labeled PS or CV), equal to 735.5 W. All three describe the same physical quantity, but picking the wrong constant shifts a result by up to 1.5%, enough to push a motor selection across a standard frame size.
The three horsepower standards
- Mechanical HP (0.7457 kW): the imperial horsepower rooted in James Watt's steam-engine work. Used on US and UK motor nameplates and in NEC Table 430.250.
- Electrical HP (0.746 kW): a rounded value adopted for electric machinery calculations in North America. It differs from mechanical HP by under 0.05%, small enough that most electricians treat the two as interchangeable.
- Metric HP / PS / CV (0.7355 kW): defined as the power needed to lift 75 kgf one meter per second. It appears on European, Japanese, and Korean equipment ratings, including most automotive and pump catalogs sold outside North America.
Why US and European nameplates don't match
A 15 kW motor built to IEC standards converts to about 20.40 metric PS, but the same 15 kW converts to only about 20.12 mechanical HP under the North American constant. That's a 1.4% gap, small on paper but large enough to matter when a spec sheet needs an exact HP figure for a permit or purchase order. If a European catalog lists a pump at "20 PS," don't write "20 HP" on a US drawing. Convert the PS figure back to kW first (kW = PS x 0.7355), then reconvert to whichever HP standard the paperwork requires.
Shaft output vs electrical input
Every HP figure this calculator produces describes shaft output power, the mechanical work available at the motor shaft, not the electrical power drawn from the wall. A motor pulling 10 kW from the panel delivers roughly 8.8 kW to the shaft after typical 88% motor efficiency, which is about 11.8 HP, not the 13.41 HP you'd get by converting the input kW directly. Use a motor kW or motor HP calculator when efficiency needs to be part of the math, not this straight unit conversion.
Common applications
A 150 kW EV motor converts to about 201 HP, the figure most manufacturers quote when stacking their spec sheet against a gasoline engine's horsepower rating.
European catalogs list kW; American drawings call out HP. Convert with the mechanical standard before issuing a purchase order so the frame size ordered matches the one specified.
Portable generator listings often quote engine kW separately from rated output watts. Converting engine kW to HP lets you check the manufacturer's advertised horsepower figure.
Fluid-handling equipment sold internationally often carries a metric PS rating on the pump curve and an HP rating on the motor. Converting both to the same standard confirms they actually match.
Common mistakes
Measuring 10 kW at the panel does not mean 13.41 HP reaches the shaft. After typical 88% motor efficiency, only about 8.8 kW (11.8 HP) is delivered mechanically.
A 20 PS European rating is about 19.7 mechanical HP, not 20. Always convert PS back to kW first, then to the HP standard your paperwork requires.
Using 1.3 instead of 1.341 as the kW-to-HP multiplier introduces over 3% error, enough to push a calculated HP figure across a standard motor frame boundary.
A spec sheet that just says '50 HP' is ambiguous by up to 1.5% depending on whether it means mechanical, electrical, or metric horsepower. State the standard alongside the number.
Frequently asked questions
Is 1 kW more than 1 HP?+
Yes. 1 kW equals about 1.34 mechanical HP, 1.34 electrical HP, or 1.36 metric HP depending on the standard used.
Why are there three different horsepower definitions?+
They come from three separate engineering traditions. Mechanical HP (0.7457 kW) traces back to James Watt's steam-engine benchmark, electrical HP (0.746 kW) was rounded for North American electrical machinery, and metric HP or PS (0.7355 kW) was defined for European and Japanese equipment. All three sit within 1.5% of each other.
Is metric horsepower the same as mechanical horsepower?+
No. Metric PS equals 735.5 W while mechanical HP equals 745.7 W, a 1.4% difference. A 100 PS engine is about 98.6 mechanical HP, not 100.
Which HP standard should I use for a US motor nameplate?+
Use mechanical or electrical HP. Both are within 0.05% of each other and match the values in NEC Table 430.250 and standard NEMA frame charts.
How many HP is a 150 kW EV motor?+
About 201 HP using the mechanical standard (150 / 0.7457), the figure most EV spec sheets quote when comparing against a combustion engine.
How many HP is a 37 kW motor?+
About 49.62 HP, which is why 37 kW motors are marketed as the metric equivalent of a 50 HP frame size in North America.
Does electrical HP differ much from mechanical HP?+
Barely. Electrical HP is fixed at 746 W versus 745.7 W for mechanical HP, a difference of about 0.04%, small enough to ignore for almost all sizing work.
Should I convert shaft output or electrical input kW to HP?+
Convert shaft output kW. This calculator's result is mechanical output power. If you only know the electrical input kW, divide by the motor's efficiency first to estimate shaft kW before converting to HP.
Is horsepower still printed on modern motor nameplates?+
Yes, alongside kW. Most NEMA and IEC nameplates list both units so the motor can be specified correctly on either side of the Atlantic.
Why does a European 15 kW motor list a different HP than a US 15 kW motor?+
Because of the standard used, not the motor. The same 15 kW converts to about 20.40 metric PS but only about 20.12 mechanical HP, a 1.4% gap caused purely by the conversion constant.