Power Converter
Convert between watts, kilowatts, megawatts, horsepower, and more power units.
Each step along the axis is ten times the one before — the power units span 10 orders of magnitude, so a straight scale would bunch almost all of them at one end.
Instant insight
That is about the same as a standby LED
1 watts — Under a watt.
Anchors like this are the quickest way to catch an answer that is out by a factor of ten.
Power is a rate; energy is an amount
A 2 kW heater running for three hours uses 6 kWh. Watts say how fast, watt-hours say how much — bills are in the second.
If a figure is meant to be a total, it should carry a time unit. A bare watt figure never is.
Check the direction of the conversion
Going from watt to kilowatt, the number should get bigger if the new unit is smaller, and smaller if it is bigger.
If it moved the wrong way, the factor has been applied upside down — the most common conversion error there is.
Worked out in your browser — nothing is sent anywhere. Comparison figures are approximate.
Common conversions
Quick Reference — 1 unit = ? Kilowatt (kW)
| Unit | Value |
|---|---|
| Watt (W) | 0.001 |
| Kilowatt (kW) | 1 |
| Megawatt (MW) | 1000 |
| Gigawatt (GW) | 1000000 |
| Horsepower (mechanical) | 0.7457 |
| Horsepower (metric) | 0.735499 |
| BTU per Hour (BTU/h) | 0.00029307 |
| Calorie per Second (cal/s) | 0.004184 |
Formula
Multiply by (from factor / to factor)
Everyday Uses
Engine specs
European cars quote kW, American listings quote horsepower — convert (1 kW ≈ 1.34 hp) to compare engines honestly.
AC and heating sizing
Air conditioners quote BTU/h, generators quote watts — convert power ratings so equipment matches the room.
Generator planning
Sum your devices' watt ratings and convert to kW or kVA to size a backup generator properly.
Fitness power
Cycling watts, treadmill horsepower, and calorie burn rates — convert power figures across your training tools.
Engine output
Compare a car quoted in horsepower against one in kilowatts — different markets use different units for the same engine.
Appliance ratings
Convert watts to horsepower or BTU/hr when comparing motors, heaters or air conditioners.
Frequently Asked Questions
How many watts are in a horsepower, and what is the difference between mechanical and metric HP?
1 mechanical (imperial) horsepower = 745.7 watts. 1 metric horsepower (PS/CV) = 735.499 watts — about 1.4% less. The difference is small enough that most people use them interchangeably. Car engine power is often listed in both: a 200 PS engine = 200 × 0.7355 = 147.1 kW = 197.2 mechanical HP. The term "horsepower" was coined by James Watt in the 1780s to market steam engines — 1 HP was defined as the power of a horse lifting 33,000 pounds one foot per minute.
How do watts, kilowatts, and megawatts compare in real-world terms?
1 watt (W) = 1 joule/second. Power scale reference: LED bulb: 5–10 W. Human at rest: ~80 W. Human cycling hard: ~200–400 W. Kettle: 2–3 kW. Electric car motor: 50–300 kW. A 200 HP car engine = ~149 kW. Large wind turbine: 2–15 MW. Nuclear power plant unit: ~1,000–1,700 MW (1–1.7 GW). UK total electricity demand: ~30–40 GW. Lightning bolt: ~1–5 GW (for ~1 microsecond = very little total energy).
What is the difference between power and energy?
Power is the rate of energy transfer (watts = joules per second). Energy is the total amount transferred over time (joules, kWh). They are related by: Energy = Power × Time. A 1 kW heater running for 1 hour consumes 1 kWh of energy. A 2 kW heater running for 30 minutes also consumes 1 kWh. Electricity bills charge for energy (kWh, not kW). A high-power device (microwave: 1,000 W) used briefly may cost less than a lower-power device (fridge: 150 W) running continuously.
How do you convert horsepower to kilowatts for car comparisons?
kW = HP × 0.7457 (mechanical HP) or HP × 0.7355 (metric PS). To convert kW to HP: divide by 0.7457. Examples: 150 HP = 111.9 kW; 200 HP = 149.1 kW; 300 HP = 223.7 kW; 400 HP = 298.3 kW. Electric cars are usually rated in kW (or sometimes kW converted to HP for marketing): Tesla Model 3 Long Range = 283 kW = 379 HP. Torque is measured separately (in lb-ft or Nm) and is equally important for real-world performance.
What is BTU/hour and how is it used for air conditioners and heating?
1 BTU/h = 0.29307 watts. Air conditioning and heating capacity is traditionally rated in BTU/h in North America. Common AC sizes: 5,000 BTU/h = 1.47 kW (small room); 12,000 BTU/h = 3.52 kW = 1 "ton" of refrigeration (the cooling equivalent of melting one ton of ice per day); 24,000 BTU/h = 7 kW (large room/small house). Boilers and furnaces: a 100,000 BTU/h boiler = 29.3 kW. Europe uses kW for heating and cooling capacity instead of BTU/h.