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Convert hp to watts

1 horsepower (mechanical) equals 745.69987 watts. Enter a value below to convert instantly.

Horsepower to watts converts an engine or motor rating into SI. One mechanical horsepower is 745.6999 watts. If the source figure is European and written PS, CV or ch, it is metric horsepower at 735.5 W instead — about 1.4% smaller.

1 hp
745.69987 W

Multiply the number of horsepower (mechanical) by 745.699871582 to get watts. How this is calculated

Copy link puts your number after the #, which browsers never send to a server — but the link itself carries it, so anyone you send it to sees the value. Save keeps the unit pair in this browser only; clear it any time from your saved list.

Need the other direction? Convert watt to horsepower (mechanical) →

Formula

Multiply the number of horsepower (mechanical) by 745.699871582 to get watts.

Step by step

  1. Start with 1 hp.
  2. Multiply by the conversion factor 745.699871582.
  3. 1 × 745.699871582 = 745.69987 W.

Horsepower (mechanical) to Watts conversion table

Horsepower (mechanical) (hp) Watts (W)
1 745.69987
2 1,491.3997
5 3,728.4994
10 7,456.9987
20 14,913.997
50 37,284.994
100 74,569.987
500 372,849.94
1,000 745,699.87

Where horsepower (mechanical) and watts are used together

Vehicle power ratings

A car advertised at 150 kW is 201 mechanical hp but 204 metric hp (PS). European manufacturers quote PS, US ones quote hp, and the same engine therefore has two different headline numbers.

Electric motors

Motor nameplates give output in kW or hp depending on the market. Note that the nameplate figure is mechanical output, not electrical input — the input is higher by whatever the efficiency is, so converting the rating does not tell you the supply load.

Appliances and tools

Vacuum cleaners, compressors and power tools are sold on wattage in metric markets and horsepower in the US. Compressor 'peak horsepower' figures in particular are marketing numbers rather than continuous ratings.

Cycling and fitness power

Athletic power output is measured in watts — a fit cyclist sustains 200–300 W. Expressing that as roughly 0.3 hp is a useful sanity check on how much power a horsepower actually is.

Everyday horsepower (mechanical) worth knowing

Values people actually look up, with the reason each one comes up. Every figure is calculated with the same engine as the converter above.

Horsepower (mechanical) (hp) Watt (W) What it is
1 745.69987 The base conversion
2 1,491.3997 A small compressor
5 3,728.4994 A workshop motor
50 37,284.994 A small engine
100 74,569.987 A small car engine
150 111,854.98 A mid-size car engine
200 149,139.97 A powerful car engine
400 298,279.95 A performance car engine

How these two units are defined

The watt is the SI unit of power: one joule per second. Mechanical horsepower was defined by James Watt as 550 foot-pounds-force per second, which works out to 745.6999 W. Metric horsepower was defined instead as 75 kilogram-force metres per second, giving 735.49875 W. A third unit, electrical horsepower, is defined as exactly 746 W for motor ratings. All three are called 'horsepower' in ordinary speech, and a specification that does not say which one it means is ambiguous by about 1.5%.

Rounding and precision

The definitional factor is exact, but the input rarely is: published engine outputs are measured to a test standard with its own tolerance, and 'peak' figures for consumer appliances may not correspond to any sustained output at all. Round converted power to three significant figures at most, and always state which horsepower you mean — the 1.4% gap between mechanical and metric hp is larger than the precision most people quote.

Mistakes people make with this conversion

  • Mixing mechanical hp with metric PS

    150 PS is 147.9 mechanical hp. European and US specifications for the same engine differ by this amount, and neither is wrong — they are different units.

  • Confusing motor input with output

    A motor rated 1 hp output at 85% efficiency draws about 877 W, not 746 W. Converting the rating gives the mechanical output only.

  • Treating peak horsepower as continuous

    Consumer compressors and vacuums often advertise a momentary peak that the motor cannot sustain. Converting that number produces a watt figure with the same problem.

Read more about these units

Sources for this page

  1. SI Brochure — The International System of Units (SI), 9th edition BIPM (Bureau International des Poids et Mesures) · Definitions of the SI base and derived units, and the SI prefixes.
  2. Special Publication 811 — Guide for the Use of the International System of Units (SI) NIST (US National Institute of Standards and Technology) · Conversion factors between US customary and SI units, and the rounding and significant-figure conventions this site follows.

Content on this page last reviewed 12 August 2026. Spotted an error? Report it — see also how these values are calculated.

Convert Horsepower (mechanical) to other power units

1 hp expressed in every other power unit on this site.

  • Watt W 745.69987
  • Kilowatt kW 0.74569987
  • Megawatt MW 0.00074569987
  • Gigawatt GW 7.4569987e-7
  • Terawatt TW 7.4569987e-10
  • Milliwatt mW 745,699.87
  • Microwatt µW 745,699,870
  • Nanowatt nW 745,699,870,000
  • Picowatt pW 745,699,870,000,000
  • Femtowatt fW 7.4569987e+17
  • Attowatt aW 7.4569987e+20
  • Centiwatt cW 74,569.987
  • Deciwatt dW 7,456.9987
  • Dekawatt daW 74.569987
  • Hectowatt hW 7.4569987
  • Petawatt PW 7.4569987e-13
  • Exawatt EW 7.4569987e-16
  • Volt-ampere VA 745.69987
  • Kilovolt-ampere kVA 0.74569987
  • Joule per Second J/s 745.69987
  • Kilojoule per Second kJ/s 0.74569987
  • Joule per Hour J/h 2,684,519.5
  • Megajoule per Second MJ/s 0.00074569987
  • Gigajoule per Second GJ/s 7.4569987e-7
  • Terajoule per Second TJ/s 7.4569987e-10
  • Petajoule per Second PJ/s 7.4569987e-13
  • Exajoule per Second EJ/s 7.4569987e-16
  • Hectojoule per Second hJ/s 7.4569987
  • Dekajoule per Second daJ/s 74.569987
  • Decijoule per Second dJ/s 7,456.9987
  • Centijoule per Second cJ/s 74,569.987
  • Millijoule per Second mJ/s 745,699.87
  • Microjoule per Second µJ/s 745,699,870
  • Nanojoule per Second nJ/s 745,699,870,000
  • Picojoule per Second pJ/s 745,699,870,000,000
  • Femtojoule per Second fJ/s 7.4569987e+17
  • Attojoule per Second aJ/s 7.4569987e+20
  • Joule per Minute J/min 44,741.992
  • Kilojoule per Hour kJ/h 2,684.5195
  • Kilojoule per Minute kJ/min 44.741992
  • Erg per Second erg/s 7,456,998,700
  • Horsepower (metric) PS 1.0138697
  • Horsepower (electric) hp(E) 0.99959768
  • Horsepower (boiler) hp(S) 0.076018133
  • Horsepower (water) hp(water) 0.99954007
  • BTU per Hour BTU/h 2,544.4336
  • BTU per Minute BTU/min 42.407226
  • BTU per Second BTU/s 0.7067871
  • MBTU per Hour MBTU/h 2.5444336
  • MMBTU per Hour MMBTU/h 0.0025444336
  • Ton of Refrigeration RT 0.21203613
  • Calorie (th) per Second cal(th)/s 178.22655
  • Kilocalorie (th) per Hour kcal(th)/h 641.61557
  • Kilocalorie (th) per Minute kcal(th)/min 10.693593
  • Kilocalorie (th) per Second kcal(th)/s 0.17822655
  • Calorie (th) per Hour cal(th)/h 641,615.57
  • Calorie (th) per Minute cal(th)/min 10,693.593
  • Calorie (IT) per Second cal(IT)/s 178.10735
  • Calorie (IT) per Minute cal(IT)/min 10,686.441
  • Calorie (IT) per Hour cal(IT)/h 641,186.48
  • Kilocalorie (IT) per Second kcal(IT)/s 0.17810735
  • Kilocalorie (IT) per Minute kcal(IT)/min 10.686441
  • Kilocalorie (IT) per Hour kcal(IT)/h 641.18648
  • BTU (th) per Hour BTU(th)/h 2,546.1364
  • BTU (th) per Minute BTU(th)/min 42.435606
  • BTU (th) per Second BTU(th)/s 0.7072601
  • Foot-pound per Second ft·lbf/s 550
  • Foot-pound per Minute ft·lbf/min 33,000
  • Foot-pound per Hour ft·lbf/h 1,980,000
  • Kilogram-force Meter per Second kgf·m/s 76.040225
  • Poundal-foot per Second pdl·ft/s 17,695.727

About the horsepower (mechanical)

The horsepower (mechanical) (hp) is a Imperial unit of power. 550 foot-pounds-force per second — the standard hp used in the US and UK.

About the watt

The watt (W) is a SI unit of power.

Related conversions

Frequently asked questions

Is PS the same as hp?

No. PS (Pferdestärke) is metric horsepower at 735.49875 W, while hp normally means mechanical horsepower at 745.6999 W. A 200 PS engine is 197.2 hp.

What is 150 hp in kilowatts?

150 mechanical hp is 111.9 kW. If the source figure was actually 150 PS, the answer is 110.3 kW instead.

Why does an engine's kW rating look so much smaller?

Because a kilowatt is about 1.34 horsepower, so the metric number is roughly three quarters of the imperial one. Nothing about the engine changes — only the unit.

How many watts are in a horsepower (mechanical)?

One horsepower (mechanical) equals 745.69987 watts.

How do you convert horsepower (mechanical) to watts?

Multiply the number of horsepower (mechanical) by 745.699871582 to get watts.

What is 1 watt in horsepower (mechanical)?

One watt equals 0.0013410221 horsepower (mechanical).

When would I convert horsepower (mechanical) to watts?

This conversion is common when engines, appliances, solar panels, and HVAC sizing.