How do you convert Watt to Horsepower (Electric)?

Multiply the value in Watt (W) by the conversion factor to get the result in Horsepower (Electric) (hp).

Convert Watt to Horsepower (Electric) (W to hp)

Reference ID: EC-POWE-WHP | EngConverter Calculation Guide

Convert From (Watt):

Result To (Horsepower (Electric)):

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Understanding Watts and Electric Horsepower

Power is the rate at which energy is transferred or converted. In the International System of Units (SI), the standard unit of power is the watt (symbol W), defined as one joule per second: \(1\,\text{W}=1\,\text{J}\,\text{s}^{-1}\).

In many engineering fields, especially when dealing with electric motors and generators, the electric horsepower (symbol hp) is still widely used. One electric horsepower is defined as exactly 746 watts: \(1\,\text{hp}=746\,\text{W}\). This legacy unit originates from the era of steam engines and provides a convenient way to compare motor output to familiar mechanical power levels.

Practical Applications

Electrical design: Selecting motor sizes for pumps, fans, and conveyors often requires converting between watts (as rated on datasheets) and horsepower (as specified by equipment manufacturers).
Energy auditing: Converting appliance power consumption from watts to horsepower helps non‑technical stakeholders grasp the magnitude of loads.
Heat flow calculations: In HVAC and thermal engineering, power expressed in watts can be related to heat transfer rates, while horsepower may be used to size compressors.

The conversion factor from watts to electric horsepower is:

\(1\,\text{W}=0.0013404825737265416\,\text{hp}\)

Because the factor is a small decimal, it is often rounded to 0.00134 hp per watt for quick hand calculations.

Watt to Horsepower (Electric) Conversion Reference Table

Watt (W)	Horsepower (Electric) (hp)
0.1	1.3405e-04
0.5	6.7024e-04
1.0	0.0013
2.0	0.0027
5.0	0.0067
10.0	0.0134
20.0	0.0268
50.0	0.067
100.0	0.134
500.0	0.6702
1000.0	1.3405

Step‑by‑Step Conversion Example

Convert 10 watts to electric horsepower.

Write down the known value and the conversion factor:

\(P_{\text{W}} = 10\,\text{W}\)

\(1\,\text{W}=0.0013404825737265416\,\text{hp}\)

Multiply the power in watts by the factor:

\[\begin{aligned} P_{\text{hp}} &= 10\,\text{W}\times 0.0013404825737265416\,\frac{\text{hp}}{\text{W}}\\ &= 0.013404825737265416\,\text{hp} \end{aligned}\]

Round to a sensible number of significant figures (e.g., 4):

\(P_{\text{hp}} \approx 0.0134\,\text{hp}\)

The exact factor is derived from the definition 1 hp = 746 W, so 1 W = 1/746 hp = 0.0013404825737265416 hp. Rounding to 0.00134 loses the last few decimal places, which is acceptable for most engineering estimates but can introduce small errors in high‑precision calculations.

Use watts when dealing with electrical systems, power quality, or when the equipment follows SI standards (e.g., datasheets, international codes). Use horsepower when the end‑user or industry convention prefers mechanical power units, such as in automotive, marine, or legacy industrial equipment catalogs.

"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison."
"Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house."
— Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)