Convert W to hp watts ↔ horsepower Free Online Secure
Type a value in watts and read it in horsepower at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert W to hp (watts ↔ horsepower)
| W | hp |
|---|---|
| 1 | 0.0013410220896 |
| 2 | 0.00268204417919 |
| 3 | 0.00402306626879 |
| 5 | 0.00670511044798 |
| 10 | 0.013410220896 |
| 20 | 0.0268204417919 |
| 50 | 0.0670511044798 |
| 100 | 0.13410220896 |
Where these units come from
Horsepower is a sales figure that outlived its sales pitch. In the 1780s James Watt needed to tell mill owners what his steam engine was worth in the only terms they knew, so he measured what a horse could haul and rounded it to 33,000 foot-pounds a minute. The watt was named after him a century later and is the SI unit, defined with no animals involved: one joule every second. The two have never quite agreed, and Europe added a third — metric horsepower, the PS or CV that European engines are rated in, which is about 1.4% smaller than the mechanical horsepower used on this page.
Where you meet them
Watts and kilowatts measure everything that consumes or produces power: kettles, motors, heat pumps, solar panels, amplifiers, data centres. Horsepower survives almost entirely in engines — cars, boats, tractors and outboards — where it is less a measurement than a way of talking. Electric cars have put the two side by side on the same spec sheet, which is where most people now notice that one number has to be converted into the other.
Questions people ask
Which horsepower does this page use?
Mechanical horsepower, 550 foot-pounds per second, which works out to about 745.7 watts. European engines are usually rated in metric horsepower — written PS, CV, ch or pk — which is 735.49875 watts exactly, roughly 1.4% smaller. A car advertised as 150 PS is about 148 mechanical hp. The difference is small but it is not rounding, and it always flatters the metric figure.
Why are kettles in watts and car engines in horsepower?
Only habit. They are the same quantity, and a 2 kW kettle and a 2.7 hp kettle would be the same appliance. Electricity arrived already metric and was never named after a horse; engines arrived with Watt's own sales figure attached and kept it. The conversion is exact in the sense that the definition is fixed — nothing is measured at the point of conversion.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Watts to horsepower: what a cyclist, a rower and an e-bike really put out
Human power and small electric vehicles are measured in watts, yet the comparison people reach for is the horse: how many horsepower is a Tour de France climber, a sprinter, a hand-cranked radio, or the 750-watt motor that American law allows on an electric bicycle? To convert W to hp, multiply by 0.00134102: 100 W is 0.134 hp, 250 W is 0.335 hp, 750 W is 1.006 hp and 2,000 W is 2.68 hp. The calculator above multiplies as you type, and the sections below show what the figures mean for riders, rowers, e-bikes and a few household gadgets.
The page gives the rule with worked examples, a profile of each unit, a comparison and a long run of sport and mobility cases, followed by the usual slips. The calculation runs in your browser and nothing you type is sent anywhere. Training zones and medical limits should come from a coach or a doctor.
How to convert W to hp: multiply by 0.00134102
The rule
One mechanical horsepower is 745.7 watts, so one watt is 0.00134102 hp. To convert W to hp, multiply the watts by 0.00134102: 150 W gives 0.201 hp, 420 W gives 0.563 hp and 1,500 W gives 2.01 hp. To go the other way, multiply hp by 745.7.
Worked examples
A recreational rider at 150 W is producing a fifth of a horsepower. A professional climber at 420 W is producing 0.56 hp. An e-bike motor of 500 W has 0.67 hp, and a hoverboard with two 250 W motors the same.
Watts per kilogram
Cyclists talk of watts per kilogram. A 70 kg rider at 3 W/kg gives 210 W, 0.28 hp, and at 6 W/kg gives 420 W, 0.56 hp. A heavier rider needs more watts to climb at the same speed, so the hp figure alone is not the whole story.
A quick sanity test
The answer in hp is more than 700 times smaller than the watt figure. If a “convert W to hp” calculation gave a larger number than you started with, you multiplied by 745.7 instead of 0.00134102.
The watt
The unit on the power meter
The watt is one joule per second. Cycling power meters, rowing ergometers and e-bike motor labels all state output in it, and so do the laws that cap the size of an electric bicycle motor in most countries.
Where it appears
Sport, light electric vehicles, small appliances and chargers.
Horsepower
The yardstick everyone understands
One mechanical horsepower is 745.7 W, close to what a draught horse could sustain. It is a handy yardstick for explaining how strong a human or a small motor is, even where nobody sells anything in it.
Where it appears
American law, popular science and the way sport is described to a general audience.
Watts against hp
One hp is 745.7 W, so the figure in hp is more than 700 times smaller. 500 W is 0.67 hp and 1,000 W is 1.34 hp. They measure the same power; only the scale differs.
The conversion is exact. The commonest trap is mixing the power at the pedals or shaft with the power drawn from a battery or a socket.
Where the conversion shows up
Cycling and rowing
A fit amateur holds about 250 W for an hour, 0.335 hp. A professional time-trialist may hold 400 to 450 W, 0.54 to 0.60 hp, and an elite rower averages about 450 W over 2,000 metres, 0.60 hp. In a sprint, riders reach 1,500 to 2,000 W, 2.0 to 2.7 hp, for a few seconds. A “convert W to hp” calculation puts these on the horse's scale.
Electric bicycle laws
The European Union and Britain cap the continuous rated power of a pedal-assisted electric bicycle at 250 W, 0.335 hp. Canada allows 500 W, 0.67 hp. Federal law in the United States defines a low-speed electric bicycle as one with a motor under 750 W, 1 hp.
The cost of speed
Air resistance grows with the cube of speed. A rider on a road bike needs about 140 W (0.19 hp) at 30 km/h and about 300 W (0.40 hp) at 40 km/h, more than double for a third more speed. This is why a motor of 250 W helps a lot at 25 km/h and very little at 40.
Power meters on bicycles
Crank and pedal power meters measure to within one or two per cent. A rider with a 260 W average over an hour has done 936 kJ of work, 0.26 kWh, about 0.35 hp-hours. The calories needed are four times that, because the human body is roughly 25 per cent efficient.
Kitchen and small tools
A stand mixer of 325 W has 0.44 hp and a hand blender of 200 W 0.27 hp. A cordless drill supplies roughly 300 to 500 W at the chuck, 0.4 to 0.7 hp. All of these figures are electrical, so the work they do at the shaft is some 20 to 40 per cent lower.
Light bulbs as a yardstick
One horsepower would power 12 incandescent bulbs of 60 W or 75 LED bulbs of 10 W. An American home lit by 30 LED lamps at 10 W uses 300 W, 0.4 hp. The comparison shows how little power good lighting needs next to heating or traction.
Lifting with a horsepower
One horsepower lifts 76 kg at one metre per second, because 745.7 W divided by 9.81 is 76 kg. A winch of 1 kW, 1.34 hp, therefore raises 102 kg at 1 m/s, or 10 kg at 10 m/s. A “convert W to hp” calculation tells you the load on a motor before you consider gearing.
Drones
A small photography drone hovers on about 150 to 250 W, 0.2 to 0.33 hp. A larger cargo drone uses 2 kW, 2.7 hp. The flight time is determined by battery energy divided by that power, which is why a 100 Wh pack gives about 25 minutes at 250 W.
Computers and devices
A laptop uses 30 to 60 W, 0.04 to 0.08 hp, a gaming PC 400 W, 0.54 hp and a server rack 10 kW, 13.4 hp. A phone charger at 20 W is 0.027 hp. Data-centre planners prefer kW and MW, and the hp figures help only in explaining the scale to a general audience.
A worked example
A 75 kg rider wants to climb a hill at 20 km/h up a 6 per cent grade. The climbing power is 75 × 9.81 × (20 / 3.6) × 0.06 = 245 W, plus about 40 W of drag and friction, 285 W in all, 0.38 hp. An e-bike with a 250 W assist would take most of the load off the rider.
The mental shortcut
To convert W to hp in your head, divide by 750 and add half a per cent. For 600 W: 600 / 750 = 0.8, and the correction brings it to 0.804, against the exact 0.8046. Without the correction the error is 0.6 per cent.
Spreadsheet formulas
In a spreadsheet, put the watts in column A and use =A2*0.00134102 in column B. For metric horsepower use =A2*0.00135962. The reverse is =B2*745.7. A column that divides the watts by 1000 gives kW and acts as a cross-check.
Rounding in sport reports
Power meters read to the nearest watt, but real variation from one pedal stroke to the next is much larger. Quote hp to two decimals at most. 285 W is 0.38 hp, not 0.38219, and a statement of three significant figures is more than the meter itself supports.
Landmarks to memorise
100 W is 0.134 hp. 250 W is 0.335 hp. 500 W is 0.67 hp. 750 W is 1.006 hp. 1,500 W is 2.01 hp. 3,000 W is 4.02 hp. With these landmarks nearly every mental convert W to hp is possible.
The body as an engine
A person running at about 600 kcal an hour is turning over 697 W of chemical energy, 0.93 hp. About 75 per cent leaves as heat, and about 175 W, 0.23 hp, is useful mechanical output. The horsepower figure for a human is therefore always far below the metabolic rate.
Reference ladder
35 W: 0.047 hp. 120 W: 0.161 hp. 320 W: 0.429 hp. 560 W: 0.751 hp. 1,200 W: 1.609 hp. 2,800 W: 3.755 hp. A table like this lets you test a calculator output at a glance.
Checking by reversing
To check a “convert W to hp” calculation result, multiply the answer by 745.7. If 320 W gave 0.429 hp, then 0.429 × 745.7 = 319.9. A second test is size: the hp figure must be more than 700 times smaller than the watts.
Link to calories and BTU
One watt is 3.412 BTU per hour, 0.86 kcal per hour and 0.7376 ft·lbf per second. A rider at 250 W therefore generates mechanical work equal to 215 kcal an hour, while the body burns about 860 kcal to do it.
Two routes to one answer
You can multiply the watts by 0.00134102 directly, or go through kilowatts: divide by 1,000 and multiply by 1.341. A third route divides by 745.7. If the routes disagree, a digit was copied wrongly.
Weightlifting and jumping
A lifter who raises a 150 kg barbell by one metre in 0.7 seconds produces an average of 150 × 9.81 × 1.0 / 0.7 = 2,100 W, 2.8 hp, and the peak is higher still. Strength sports are short bursts at several horsepower, which no rider or runner can sustain for more than a second or two. A “convert W to hp” calculation sets these bursts next to the steady output of an endurance athlete.
Hiking up a mountain
A hiker weighing 80 kg with a pack who climbs 1,000 metres in three hours does 80 × 9.81 × 1,000 / 10,800 = 73 W of climbing work, 0.098 hp, on top of the effort of walking. The figure looks small, yet the body burns four times that as fuel, and a “convert W to hp” calculation on the metabolic rate would give about 0.4 hp.
Heart and brain
The heart does mechanical work of about 1.3 W on average, 0.0017 hp, even though it burns more than that. The brain uses about 20 W, 0.027 hp, a little more than a quarter of a per cent of one horse. A person at rest runs on 80 to 100 W in total, mostly heat.
Time trial against climb
A professional climbing a long mountain at 6 W/kg for 40 minutes, with a 65 kg frame, gives 390 W, 0.52 hp. On the flat, a team time trial at 50 km/h needs about 550 W per rider, 0.74 hp, because of the cubic rise in air drag, though riders in a line shelter one another.
Stair climbing
Running up 3 metres of stairs in 10 seconds, a 70 kg person generates 70 × 9.81 × 3 / 10 = 206 W, 0.28 hp. Over a minute, that effort is about 12 kJ. Stair races in tall buildings are exercises in sustaining a quarter of a horsepower for several minutes.
Hand-cranked and pedal generators
A hand crank gives 20 to 30 W, 0.027 to 0.040 hp, for a few minutes. A pedal generator gives 75 to 100 W, 0.10 to 0.13 hp, for an hour. A 100 W bulb, 0.134 hp, would take all of a person's output. Hand-cranked radios and lanterns use LEDs for this reason.
Treadmill motor claims
A treadmill advertised at 3.0 continuous hp is claiming 2.24 kW at the motor shaft. A 15 A circuit at 120 V supplies at most 1.8 kW, and only 1.44 kW continuously, so the claim cannot be literally true. The honest comparison is in amps, or in the kW drawn from the wall.
Electric scooters and hoverboards
A rental e-scooter has about 250 to 350 W, 0.34 to 0.47 hp, a performance model 1,000 W, 1.34 hp, and a hoverboard two motors of 250 W, 0.67 hp in all. German rules for e-scooters cap continuous power at 500 W. The same number in hp is 0.67, a figure marketing seldom uses.
Mid-drive and hub motors
An e-bike hub motor of 250 W has 0.34 hp, one of 500 W 0.67 hp and a mid-drive of 750 W 1.0 hp. The peak output may be double the rated figure for a few seconds. Mountain-bike motors of 250 W nominal can reach 600 W peak, 0.8 hp.
Battery size and range
A 500 Wh battery lasts one hour at 500 W, 0.67 hp, and ten hours at 50 W. An assisted rider using 100 W of motor power on average covers 80 km on a 500 Wh battery at 16 km/h for five hours. A “convert W to hp” calculation on the motor rating does not tell the range, because the battery energy matters.
More values for convert W to hp
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 W = 0.000134102 hp
- 0.5 W = 0.000670511 hp
- 3 W = 0.00402307 hp
- 4 W = 0.00536409 hp
- 7 W = 0.00938715 hp
- 15 W = 0.0201153 hp
- 20 W = 0.0268204 hp
- 75 W = 0.100577 hp
- 200 W = 0.268204 hp
- 500 W = 0.670511 hp
- 2,000 W = 2.68204 hp
- 10,000 W = 13.4102 hp
Common slips with a “convert W to hp” calculation
Using the wrong direction
From watts to hp the number gets smaller. If 750 W became 559,275, you used the factor for the other direction.
Mixing input and output
An e-bike motor labelled 250 W is its rated power, and a drill labelled 750 W is the electrical input. The mechanical power at the wheel or chuck is lower, so do not equate the label with a horsepower at the output.
Peak and continuous
Sprint, motor-peak and "peak hp" figures last seconds. Compare sustained numbers with sustained ones, and keep the same duration for both when you rank riders or motors.
Short answers
How do I convert W to hp?
Multiply the watts by 0.00134102.
How many hp is 750 W?
1.006 hp.
How many hp is 250 W?
0.335 hp.
How many watts in 1 hp?
745.7 W.
Does my number leave my device?
No, the calculation runs in your browser.
More pages and a wrap-up
For other power conversions see Convert kW to hp, Convert hp to kW, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert mph to knots, Convert pt to qt, Convert L/100km to MPG (US). For the opposite direction see Convert hp to W.
In short, a “convert W to hp” calculation means one multiplication by 0.00134102 and a unit written next to the result. Your figure is calculated locally, with no account and no upload.