Free tool
HP to kW Calculator
Horsepower times 0.746 is the kilowatts at the shaft. What a motor draws from the supply is larger by its efficiency — and the service factor is an allowance, not the rating.
kW = hp × 0.746
kW = hp × 746 ÷ 1,000. 5 hp is 3.73 kW; 10 hp is 7.46 kW. For metric horsepower (PS) use 735.5 W, so 100 PS is 73.55 kW.
That is shaft output. A 5 hp motor at 88% efficiency draws about 4.24 kW from the supply. The inverse is the kW to hp calculator.
The rating
Enter ¾ hp as 0.75.
From the nameplate, not a guess.
“SF” on the plate. Blank if none.
The answer
Shaft output
3.73 kW
kW = hp × 746.0 ÷ 1,000 → 5.00 × 746.0 ÷ 1,000
What the motor draws at full load
Electrical input ≈ 4.24 kW (3.73 ÷ 0.88), of which about 0.51 kW is lost as heat in the motor. Reading the shaft figure as the supply load would understate it by 12%.
Current follows the input, not the shaft figure — convert it with the kW to amps calculator and a power factor.
What this does not tell you
Motor circuit sizing. NEC Article 430 sizes motor branch circuits from its full-load current tables by horsepower and voltage, not from a converted kW. Starting draw. A motor starting across the line draws several times its running current for a moment; that is not in a kW conversion. A generator or battery pick — conversion alone is not a size.
Informational use only, please verify before you rely on it
This reproduces the standard definitions of electrical horsepower (746 W), mechanical horsepower (550 ft·lbf/s, about 745.7 W) and metric horsepower (about 735.5 W), and the relationship electrical input = shaft output ÷ efficiency. It is a unit conversion, not a determination. It does not select motors, generators or batteries, or size conductors, overcurrent protection or motor branch circuits, which NEC Article 430 governs. Confirm against the equipment nameplate and with the authority having jurisdiction.
This tool is provided for general informational and educational purposes only. Its output is an illustrative estimate generated from the values you enter and from general assumptions that will not match every deal, market, lender, or homeowner. It is not tax, legal, accounting, financial, or professional advice, and it is not a quote, an offer, a credit decision, or a guarantee of pricing, approval, timing, savings, or eligibility.
You are solely responsible for independently confirming all information presented here including any figures, rates, fees, margins, timelines, tax treatment, and federal, state, local, or utility incentives, with the applicable lender, authority having jurisdiction, and your own qualified tax, legal, and financial advisors before acting on it, relying on it, or presenting it to a homeowner or any third party. Incentive programs, lender terms, and permitting requirements change frequently and vary by jurisdiction.
Seamless Home is not a tax advisor, law firm, lender, or licensed installing contractor, and makes no representation or warranty as to the accuracy, completeness, or currency of the information produced by this tool. To the fullest extent permitted by law, Seamless Home accepts no liability for any decision made or action taken in reliance on it.
Three numbers on one motor
A motor plate carries a horsepower, an efficiency and often a service factor, and each answers a different question. The horsepower converts to the kilowatts the motor delivers. The efficiency turns that into the kilowatts it draws — the figure the supply, the meter and a kW to amps conversion care about. The service factor is how far past the rating it can be pushed under stated conditions, which is why a pool pump sold on “total horsepower” can look larger than the same motor sold on its rating.
Current also depends on power factor, which is why a motor's kVA runs above its kW — see the kW to kVA calculator and what power factor is. Going the other way from a current reading, the amps to kW calculator recovers the shaft output from what the motor draws.
Frequently Asked Questions
How do you convert hp to kW?+
Multiply horsepower by 0.746 for electrical horsepower, or by 0.7457 for mechanical (imperial) horsepower: kW = hp × 746 ÷ 1,000. 5 hp is 3.73 kW. For metric horsepower (PS) multiply by 0.7355, so 100 PS is 73.55 kW.
How many kW is 1 hp?+
0.746 kW for electrical horsepower, about 0.7457 kW for mechanical horsepower and about 0.7355 kW for metric horsepower. They are three different units, which is why a European car's PS and a US engine's hp do not match for the same engine.
How many kW does a 5 hp motor use?+
More than 3.73 kW. 5 hp is 3.73 kW at the shaft — what the motor delivers. What it draws from the supply is that divided by efficiency: at 88 percent, about 4.24 kW at full load. The difference is lost as heat in the motor.
What is 10 hp in kW?+
7.46 kW (electrical hp) or about 7.46 kW mechanical, which is why a 10 hp NEMA motor and a 7.5 kW IEC motor are treated as equivalent ratings. At 90 percent efficiency it draws about 8.29 kW electrically.
What does the service factor on a motor mean?+
It is the overload the motor is designed to tolerate under the conditions on its plate. A 1.5 hp motor with a service factor of 1.65 can tolerate about 2.47 hp. It is an allowance, not the rating. Some pool pump listings quote rated hp times service factor as total horsepower, so compare like with like.
Can I use this to size a breaker or wire for a motor?+
No. NEC Article 430 sizes motor branch circuits from its full-load current tables by horsepower and voltage, not from a converted kW or the nameplate current alone. A motor also draws several times its running current while starting.
Does the kW help size a generator or battery for a motor load?+
It is one input, not an answer. The running figure is the electrical input kW, not the shaft kW, and a motor starting across the line needs a surge well above that. A generator or battery system is sized from the whole load list, which is a separate calculation.
Related resources
kW to HP Calculator
The inverse — in all three horsepowers, with a motor's input kW read as input.
Learn more →kW to Amps Calculator
Current from the electrical input, with power factor applied.
Learn more →Amps to kW Calculator
Power from a current reading, including a motor's shaft output.
Learn more →kW to kVA Calculator
Apparent power from real power, with motor efficiency applied.
Learn more →Ratings read the way the nameplate wrote them
Seamless Home runs the design, permit and interconnection layer for the partners it works with — which is where a motor or equipment rating gets read as the figure it actually is. Coverage is confirmed per service area rather than promised as blanket availability.
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