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Use this calculator to

  • Convert motor nameplate horsepower to kW when specifying UK equipment
  • Compare imported motors rated in HP with European kW ratings
  • Pick the correct HP definition: mechanical, electrical or metric
  • Work back from a kW rating to HP for legacy spec sheets and datasheets

Horsepower to kW Converter

Convert motor power between horsepower (HP) and kilowatts (kW).

HP
Result
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kW
Result
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Formulas

  • kW = HP × 0.7457 (mechanical HP)
  • kW = HP × 0.7460 (electrical HP)
  • kW = HP × 0.7355 (metric HP)
  • W = kW × 1000

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Common scenarios

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For business

Why this matters for businesses

On most UK manufacturing and distribution sites, three or four motors do the bulk of the work. A 200 hp air compressor, a couple of 75 hp chillers, a process pump or two, and the baseload chart starts to make sense. Old nameplates quote horsepower, new procurement specs quote kW, and the conversion has to be right both ways because the difference between 200 hp (149 kW) and 200 kW shows up as a £30,000 swing in annual running cost at typical UK commercial power prices.

Motor efficiency standards have moved on too. The shift from IE2 to IE3 to IE4 across legally required ratings means that a like-for-like replacement of an older motor can quietly trim 4 to 7 percent off the running kWh, and on a 24-hour-duty compressor that is real money. A site doing a capacity audit needs accurate kW figures to scope the spend, the payback, and any energy-efficiency credit available under SECR, ESOS Phase 4, or sector-specific carbon agreements.

Purely Energy works with industrial clients on motor-heavy sites where the load profile is dominated by a few large drives, and the conversations are usually about variable-speed drive retrofits, soft starter projects, and the contract structure that captures the saving. Getting the hp-to-kW conversion right is the first step in a load-profile audit that ends with a procurement strategy aligned to how the site actually runs. The motor list, the running hours, and the diversity profile all feed into the half-hourly demand shape, and that shape is what the supplier prices against.

Common questions

How do I convert horsepower to kW?

Multiply by the factor for the HP type: kW = HP x 0.7457 for mechanical (imperial) horsepower, x 0.7460 for electrical horsepower, or x 0.7355 for metric horsepower. A 10 HP motor on the mechanical definition is about 7.46 kW, which is why it lines up with the standard European 7.5 kW motor frame size.

What is the difference between mechanical, electrical and metric horsepower?

Mechanical HP is the imperial definition of 745.7 W, used on UK and US motor nameplates. Electrical HP is rounded to exactly 746 W and appears on some electrical machine ratings. Metric HP is 735.5 W, defined from kilogram-force units, and shows up as PS or CV on continental European equipment. The differences are small but matter on larger machines.

How do I convert kW back to horsepower?

Divide by the same factor: HP = kW / 0.7457 for mechanical horsepower. A 7.5 kW motor is just over 10 HP, a 3 kW pump is about 4 HP, and a 110 kW industrial motor is roughly 147.5 HP. Use the kW to HP tab and pick the HP definition that matches the documentation you are filling in.

Is a motor's HP rating its electrical input power?

No. Horsepower and kW ratings on a motor nameplate describe mechanical output at the shaft. Electrical input is higher because no motor is 100 percent efficient: input kW = output kW / efficiency. A 7.5 kW motor at 90 percent efficiency draws about 8.3 kW electrically at full load, which is the figure that matters for supply and cable sizing.

Which HP type should I assume for a UK motor nameplate?

UK and US nameplates almost always use mechanical (imperial) horsepower, 745.7 W per HP, so that is the default selection here. If the equipment is continental European and rated in PS or CV, use metric HP instead. When precision matters, check the datasheet, because the wrong definition introduces an error of about 1.4 percent.

Related calculators

The conversions that procurement and engineering use alongside this one.

Horsepower to kW Converter | Purely Energy