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.
Power
Convert watts to hp
1 watt equals 0.0013410221 horsepower (mechanical). Enter a value below to convert instantly.
Watts to horsepower converts the SI power unit into the one engine and motor specifications still use. This page uses mechanical horsepower — 550 foot-pounds-force per second, or 745.6999 W. Metric horsepower (PS, ch, CV) is a different unit at 735.5 W, and the two are mixed up constantly in vehicle specifications.
1 W
0.0013410221 hp
Multiply the number of watts by 0.0013410220896 to get horsepower (mechanical). How this is calculated
Need the other direction? Convert horsepower (mechanical) to watt →
Formula
Multiply the number of watts by 0.0013410220896 to get horsepower (mechanical).
Step by step
- Start with 1 W.
- Multiply by the conversion factor 0.0013410220896.
- 1 × 0.0013410220896 = 0.0013410221 hp.
Watts to Horsepower (mechanical) conversion table
| Watts (W) | Horsepower (mechanical) (hp) |
|---|---|
| 1 | 0.0013410221 |
| 2 | 0.0026820442 |
| 5 | 0.0067051104 |
| 10 | 0.013410221 |
| 20 | 0.026820442 |
| 50 | 0.067051104 |
| 100 | 0.13410221 |
| 500 | 0.67051104 |
| 1,000 | 1.3410221 |
Where watts and horsepower (mechanical) are used together
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 watts 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.
| Watt (W) | Horsepower (mechanical) (hp) | What it is |
|---|---|---|
| 250 | 0.33525552 | A strong cyclist's sustained output |
| 745.6999 | 1 | Exactly one mechanical horsepower |
| 1,000 | 1.3410221 | One kilowatt |
| 2,000 | 2.6820442 | A domestic kettle |
| 5,000 | 6.7051104 | A small motor |
| 75,000 | 100.57666 | A small car engine |
| 100,000 | 134.10221 | A mid-size car engine |
| 150,000 | 201.15331 | A powerful 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
- SI Brochure — The International System of Units (SI), 9th edition
- Special Publication 811 — Guide for the Use of the International System of Units (SI)
Content on this page last reviewed 12 August 2026. Spotted an error? Report it — see also how these values are calculated.
Convert Watt to other power units
1 W expressed in every other power unit on this site.
- Watt W 1
- Kilowatt kW 0.001
- Megawatt MW 0.000001
- Gigawatt GW 1e-9
- Terawatt TW 1e-12
- Milliwatt mW 1,000
- Microwatt µW 1,000,000
- Nanowatt nW 1,000,000,000
- Picowatt pW 1,000,000,000,000
- Femtowatt fW 1,000,000,000,000,000
- Attowatt aW 1e+18
- Centiwatt cW 100
- Deciwatt dW 10
- Dekawatt daW 0.1
- Hectowatt hW 0.01
- Petawatt PW 1e-15
- Exawatt EW 1e-18
- Volt-ampere VA 1
- Kilovolt-ampere kVA 0.001
- Joule per Second J/s 1
- Kilojoule per Second kJ/s 0.001
- Joule per Hour J/h 3,600
- Megajoule per Second MJ/s 0.000001
- Gigajoule per Second GJ/s 1e-9
- Terajoule per Second TJ/s 1e-12
- Petajoule per Second PJ/s 1e-15
- Exajoule per Second EJ/s 1e-18
- Hectojoule per Second hJ/s 0.01
- Dekajoule per Second daJ/s 0.1
- Decijoule per Second dJ/s 10
- Centijoule per Second cJ/s 100
- Millijoule per Second mJ/s 1,000
- Microjoule per Second µJ/s 1,000,000
- Nanojoule per Second nJ/s 1,000,000,000
- Picojoule per Second pJ/s 1,000,000,000,000
- Femtojoule per Second fJ/s 1,000,000,000,000,000
- Attojoule per Second aJ/s 1e+18
- Joule per Minute J/min 60
- Kilojoule per Hour kJ/h 3.6
- Kilojoule per Minute kJ/min 0.06
- Erg per Second erg/s 10,000,000
- Horsepower (mechanical) hp 0.0013410221
- Horsepower (metric) PS 0.0013596216
- Horsepower (electric) hp(E) 0.0013404826
- Horsepower (boiler) hp(S) 0.000101942
- Horsepower (water) hp(water) 0.0013404053
- BTU per Hour BTU/h 3.4121416
- BTU per Minute BTU/min 0.056869027
- BTU per Second BTU/s 0.00094781712
- MBTU per Hour MBTU/h 0.0034121416
- MMBTU per Hour MMBTU/h 0.0000034121416
- Ton of Refrigeration RT 0.00028434514
- Calorie (th) per Second cal(th)/s 0.23900574
- Kilocalorie (th) per Hour kcal(th)/h 0.86042065
- Kilocalorie (th) per Minute kcal(th)/min 0.014340344
- Kilocalorie (th) per Second kcal(th)/s 0.00023900574
- Calorie (th) per Hour cal(th)/h 860.42065
- Calorie (th) per Minute cal(th)/min 14.340344
- Calorie (IT) per Second cal(IT)/s 0.2388459
- Calorie (IT) per Minute cal(IT)/min 14.330754
- Calorie (IT) per Hour cal(IT)/h 859.84523
- Kilocalorie (IT) per Second kcal(IT)/s 0.0002388459
- Kilocalorie (IT) per Minute kcal(IT)/min 0.014330754
- Kilocalorie (IT) per Hour kcal(IT)/h 0.85984523
- BTU (th) per Hour BTU(th)/h 3.4144251
- BTU (th) per Minute BTU(th)/min 0.056907085
- BTU (th) per Second BTU(th)/s 0.00094845141
- Foot-pound per Second ft·lbf/s 0.73756215
- Foot-pound per Minute ft·lbf/min 44.253729
- Foot-pound per Hour ft·lbf/h 2,655.2237
- Kilogram-force Meter per Second kgf·m/s 0.10197162
- Poundal-foot per Second pdl·ft/s 23.73036
About the watt
The watt (W) is a SI unit of power.
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.
Related conversions
Frequently asked questions
How many watts is one horsepower?
Mechanical horsepower is 745.6999 W. Metric horsepower (PS) is 735.49875 W and electrical horsepower is exactly 746 W — three different units sharing one name.
What is 100 kW in horsepower?
100 kW is 134.1 mechanical hp, or 136.0 metric hp (PS). The two figures differ by about 1.4%, which is why European and US brochures for the same car disagree slightly.
How much power does a person produce?
A fit cyclist sustains around 200–300 W, which is roughly 0.27–0.40 hp. A brief sprint can exceed 1,000 W. It is a useful reminder of how much work one horsepower represents.
How many horsepower (mechanical) are in a watt?
One watt equals 0.0013410221 horsepower (mechanical).
How do you convert watts to horsepower (mechanical)?
Multiply the number of watts by 0.0013410220896 to get horsepower (mechanical).
What is 1 horsepower (mechanical) in watts?
One horsepower (mechanical) equals 745.69987 watts.
When would I convert watts to horsepower (mechanical)?
This conversion is common when engines, appliances, solar panels, and HVAC sizing.