Watts to Horsepower Calculator
Convert watts and kilowatts to horsepower instantly, mechanical and electrical.
Convert power in watts (or kilowatts) to horsepower. Useful for electric motors, power tools, and any device rated in watts that you want to compare in HP.
Watts to HP Formula
How to Use This Calculator
- Enter the power in watts.
- Read the horsepower result, with kilowatts shown too.
Worked Example
Three Definitions of Horsepower
The watt-to-HP factor depends on which horsepower you mean. Mechanical HP = 745.7 W (the automotive standard). Electrical HP = exactly 746 W, used for motor ratings. Metric HP (PS) = 735.5 W, common in Europe. For most purposes the mechanical figure is correct, but motor nameplates often use the electrical definition — the 0.3 W difference is negligible for everyday conversions.
Common Uses for Watts-to-HP
This conversion is handy any time a device is rated in watts but you think in horsepower: electric motors, power tools, e-bike and EV drivetrains, generators, and appliances. A 1,500 W angle grinder is about 2 HP; a 3,000 W e-bike motor is roughly 4 HP. It's also the bridge between electrical power draw and mechanical output once you account for motor efficiency.
Input Watts and Output Watts Are Not the Same Thing
This is the distinction that makes or breaks the conversion in practice. A motor rated "1,500 W" could mean either of two very different things:
| Input (electrical) | Output (shaft) | |
|---|---|---|
| What it measures | Power drawn from the supply | Mechanical power delivered |
| Which is larger | Always the larger figure | Input × efficiency |
| Used for | Breaker sizing, running cost, generator sizing | Comparing against an engine's horsepower |
| 1,500 W example | 2.01 hp of electricity consumed | ≈1.6 hp of work done at 80% efficiency |
So a 1,500 W tool draws 2.01 hp worth of electricity but delivers roughly 1.6 hp at the spindle. When someone compares "my 3 kW e-bike motor" against a gasoline engine's horsepower, they are usually comparing input against output — which flatters the electric motor by 15–25%.
Beware "Peak" and "Maximum" Wattage
Consumer product marketing routinely quotes a peak figure the device cannot sustain:
- Vacuum cleaners and shop vacs — "peak horsepower" ratings are measured at stall or at instantaneous startup and can be several times the continuous figure. A "6.5 peak HP" wet/dry vac plugged into a 13 A domestic socket cannot possibly draw 4,850 W continuously; the socket would trip.
- Power tools — peak or "max watts out" versus continuous input.
- E-bike and scooter motors — a "1,000 W" motor is often 500 W nominal with a 1,000 W peak, which is what the controller allows briefly.
- Inverters and generators — surge rating versus continuous rating, sometimes double.
The honest cross-check is the supply: a device on a 230 V, 13 A plug cannot exceed roughly 3,000 W continuous, whatever the box claims. On a 120 V, 15 A circuit the ceiling is about 1,800 W.
Watts in E-Bike and Scooter Regulations
Legal classes for light electric vehicles are written in watts of continuous rated output, not peak, which is why a motor's advertised figure and its legal classification often disagree:
| Continuous rating | In horsepower | Typical classification |
|---|---|---|
| 250 W | 0.34 hp | EU pedal-assist e-bike limit |
| 500 W | 0.67 hp | Common US e-bike class limit |
| 750 W | 1.01 hp | US Class 1–3 upper limit |
| 4,000 W | 5.4 hp | Light moped territory |
| 11,000 W | 14.8 hp | EU A1 motorcycle ceiling |
Note how modest these are in horsepower — 250 W is a third of one horsepower, which is roughly what a fit cyclist sustains. For motorcycle categories see motorcycle power-to-weight, which covers the power-to-weight limits that accompany the kW caps.
Watts to HP Conversion Table
| Watts | Mechanical HP | Kilowatts |
|---|---|---|
| 746 | 1.00 | 0.75 |
| 1,500 | 2.01 | 1.5 |
| 3,000 | 4.02 | 3.0 |
| 5,500 | 7.38 | 5.5 |
| 10,000 | 13.41 | 10.0 |
Common Watts to HP Lookups
| Watts | Mechanical HP | Typical use |
|---|---|---|
| 500 | 0.67 | E-bike motor |
| 746 | 1.00 | The definition (electrical HP) |
| 1,000 | 1.34 | Small power tools |
| 1,500 | 2.01 | Household circuit max |
| 3,000 | 4.02 | Large workshop motor |
| 5,000 | 6.71 | EV onboard charger |
| 7,457 | 10.0 | Ten horsepower exactly |
Frequently Asked Questions
One mechanical horsepower equals 745.7 watts. Electrical horsepower is 746 watts and metric horsepower (PS) is 735.5 watts.
Divide the wattage by 745.7. For example, 1,500 watts ÷ 745.7 = 2.01 horsepower.
Multiply kilowatts by 1.341, or convert kW to watts first (×1000) then divide by 745.7.
Mechanical, electrical, and metric horsepower were defined slightly differently. Mechanical (745.7 W) is most common for engines; electrical (746 W) for motors.
Almost — 1,000 watts is about 1.34 horsepower, since one HP is 745.7 watts.
Appliances and power tools almost always quote input watts — electricity drawn. Industrial motors quote output shaft power. A 1,500 W tool draws 2.01 hp of electricity but delivers roughly 1.6 hp of work.
It cannot, continuously. 6.5 hp is 4,850 W, far beyond what a domestic socket supplies — about 3,000 W on a 230 V/13 A plug or 1,800 W on 120 V/15 A. "Peak" figures are measured at stall or instantaneous startup.
0.34 hp — roughly what a fit cyclist sustains. That 250 W figure is the EU continuous-rated limit for pedal assist; the motor's peak output may be considerably higher.
Mechanical (745.7 W) for anything automotive. Electrical HP is exactly 746 W and metric PS is 735.5 W. The mechanical-versus-electrical gap of 0.3 W is negligible; the PS gap of 1.4% is not.