Motor HP to kW Calculator – Convert Horsepower Instantly

⚡ Motor HP to kW Calculator

Convert horsepower to kilowatts with efficiency, service factor & load adjustments

🔧 Quick Presets

📊 Calculator Inputs

Input Mode:

Motor Power (HP)

Motor Type

Motor Efficiency (%)

Service Factor

Load Factor (%)

Power Factor (AC Motors)

Voltage (V)

Safety / Derating Factor

📊 Conversion Results

💡 Motor Power Reference Grid

0.746

kW per 1 HP

1.341

HP per 1 kW

550

ft·lbf/s per HP

745.7

Watts per HP

2545

BTU/hr per HP

33,000

ft·lbf/min per HP

76.04

kgf·m/s per HP

1.0139

Metric HP per 1 HP

📋 HP to kW Conversion Table

HP Rating	Exact kW	kW @ 85% Eff.	kW @ 90% Eff.	kW @ 95% Eff.	Watts
0.25 HP	0.187 kW	0.220 kW	0.208 kW	0.196 kW	186.4 W
0.5 HP	0.373 kW	0.439 kW	0.415 kW	0.393 kW	372.9 W
0.75 HP	0.559 kW	0.658 kW	0.621 kW	0.588 kW	559.3 W
1 HP	0.746 kW	0.877 kW	0.829 kW	0.785 kW	745.7 W
1.5 HP	1.119 kW	1.316 kW	1.243 kW	1.178 kW	1118.6 W
2 HP	1.491 kW	1.754 kW	1.657 kW	1.569 kW	1491.4 W
3 HP	2.237 kW	2.632 kW	2.486 kW	2.355 kW	2237.1 W
5 HP	3.729 kW	4.387 kW	4.143 kW	3.925 kW	3728.5 W
7.5 HP	5.593 kW	6.580 kW	6.214 kW	5.888 kW	5592.7 W
10 HP	7.457 kW	8.773 kW	8.286 kW	7.850 kW	7456.9 W
15 HP	11.185 kW	13.159 kW	12.428 kW	11.774 kW	11185.4 W
20 HP	14.914 kW	17.546 kW	16.571 kW	15.699 kW	14913.9 W
25 HP	18.642 kW	21.932 kW	20.714 kW	19.623 kW	18642.4 W
50 HP	37.285 kW	43.865 kW	41.428 kW	39.247 kW	37284.8 W
100 HP	74.570 kW	87.729 kW	82.856 kW	78.495 kW	74569.5 W

🔌 Motor Amperage Reference (Full Load Amps)

HP Rating	120V Single Phase	240V Single Phase	208V 3-Phase	240V 3-Phase	480V 3-Phase
0.5 HP	9.8A	4.9A	2.5A	2.2A	1.1A
1 HP	16.0A	8.0A	4.0A	3.5A	1.8A
2 HP	24.0A	12.0A	6.5A	5.6A	2.8A
3 HP	34.0A	17.0A	9.0A	7.8A	3.9A
5 HP	56.0A	28.0A	15.2A	13.2A	6.6A
7.5 HP	—	40.0A	22.0A	19.0A	9.5A
10 HP	—	50.0A	28.0A	24.2A	12.1A
15 HP	—	—	42.0A	36.4A	18.2A
25 HP	—	—	68.0A	59.4A	29.7A
50 HP	—	—	130.0A	112.7A	56.3A

📐 Motor Efficiency by Type & Size (NEMA Premium)

Motor HP	Standard Eff. (%)	High Eff. (%)	NEMA Premium (%)	Motor Type	Typical Application
0.5 – 1 HP	72 – 78%	80 – 84%	85 – 87%	Single Phase	Small tools, fans
1.5 – 3 HP	78 – 83%	84 – 87%	87 – 89%	Single/3-Phase	Power tools, pumps
5 – 7.5 HP	83 – 86%	87 – 90%	89 – 91%	Three Phase	Compressors, conveyors
10 – 15 HP	86 – 88%	89 – 91%	91 – 92.4%	Three Phase	HVAC, industrial
20 – 30 HP	88 – 90%	91 – 92%	92.4 – 93%	Three Phase	Large machinery
40 – 75 HP	90 – 92%	92 – 93.6%	93.6 – 94.5%	Three Phase	Heavy industrial
100+ HP	92 – 93%	93.6 – 94.5%	95 – 96%	Three Phase	Large drives, mills

📋 Common Motor Applications – Typical HP & kW Ratings

Application	Typical HP	Equivalent kW	Phase	Notes
Bench Grinder	0.5 – 1 HP	0.37 – 0.75 kW	Single	3450 RPM typical
Drill Press	0.5 – 1.5 HP	0.37 – 1.12 kW	Single	Variable speed
Table Saw	1.5 – 5 HP	1.12 – 3.73 kW	Single/3-Ph	Cabinet saws: 3-5 HP
Band Saw	1 – 3 HP	0.75 – 2.24 kW	Single	1725 or 3450 RPM
Air Compressor	2 – 25 HP	1.49 – 18.64 kW	Single/3-Ph	SF 1.15 typical
Pool Pump	0.75 – 3 HP	0.56 – 2.24 kW	Single	Variable speed saves energy
HVAC Fan/Blower	1 – 15 HP	0.75 – 11.19 kW	3-Phase	Low SF, continuous duty
Conveyor Belt	1 – 50 HP	0.75 – 37.3 kW	3-Phase	Torque-heavy start
CNC Spindle	1 – 10 HP	0.75 – 7.46 kW	3-Phase	Variable frequency drive
Lathe (Metalworking)	1 – 20 HP	0.75 – 14.91 kW	Single/3-Ph	High starting torque

💡 Tip 1 – Efficiency Matters for Real-World kW: The nameplate HP rating is the mechanical output. The electrical input kW is always higher due to losses. For a 5 HP motor at 90% efficiency, input power = (5 × 0.746) / 0.90 = 4.14 kW electrical draw. Always size wiring and breakers to the electrical input, not the mechanical output.

💡 Tip 2 – Service Factor vs. Load Factor: Service factor (SF) is a nameplate rating indicating how much overload the motor can sustain continuously without damage. Load factor is your actual operating load as a percentage of rated power. Running a 1.15 SF motor at 100% load is fine; running at 115% load briefly is acceptable. Size your motor so normal operating load is 75–90% of rated HP for longest life.

⚠️ Safety Note: Always verify wire gauge, breaker size, and motor starter ratings match the calculated electrical input current. Never exceed the nameplate rated voltage or the motor service factor continuously. Consult a licensed electrician for installations above 240V or 20A circuits.

Converting horsepower of engines to kilowatts has a built-in challenge especially when one works with electrical engines. The basic math is quite easy. To get the match of HP to kW, one multiplies the value of HP by 0.7457.

So one HP matches around 0.7457 kW. Rather, one kW matches around 1.34 HP.

How to convert HP to kW

Horsepower is a unit for power, just as is the kilowatt. Power shows the speed of energy use during a set time. Both units measure the same thing, only with different numbers.

It is like miles against kilometers. Simply other ways to measure.

There actually exist various kinds of horsepower, which can cause a bit of confusion. The mechanical horsepower, or also called imperial, matches about 745.7 watts. The metric horsepower is a bit smaller, around 735.5 watts.

Electrical horsepower measures exactly 746 watts. In the United States one tends to use the electrical horsepower, which is the imperial unit for measuring the output of electrical engines.

Here are fast samples. A motor of 2 HP matches 2 times 0.7457, so around 1.49 kW. A motor of 20 HP multiplied by 0.74 gives around 14.8 kW.

And 10 kW turns into about 13.41 HP.

Here comes the hard part. The rated power of a motor always relates to its output power. One rates engines usually during production.

Because no motor reaches 100 percent efficiency, the input electrical power needs to bee more than the rated output in kW. A common simple rule for use is, that a motor of 10 HP needs roughly 10 kW of electrical power to run. That works as a rough rule, where 1000 watts match to 1 HP for input.

Efficiency of engines plays a big role here. When one needs 7.5 kW from the outlet and the motor runs at 92 percent efficiency, the input power comes to around 8.15 kW. Engines with partial HP commonly have only around 50 percent efficiency, so they need even more input power than their name shows.

And kW is the value that ties directly to kilowatt hours on the bill, so knowing these conversions helps to estimate the costs of use. In the United States one prefers HP, while elsewhere one may use kW or PS. It depends on what one is used to.

The conversion itself stays the same, no matter the type of motor or engine. Even so electrical engines differ greatly from engines with internal burning. Electrical engines drop torque when the RPM grows, while burning engines gain torque with higher RPM.

Also RPM matters, since looking at the curves ofengines gives more complete info than only the lone HP or kW figure.

Author

Thomas Martinez

Hi, I am Thomas Martinez, the owner of ToolCroze.com! As a passionate DIY enthusiast and a firm believer in the power of quality tools, I created this platform to share my knowledge and experiences with fellow craftsmen and handywomen alike.

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