Power Converter (Horsepower to kW, PS & Watts)
Convert horsepower to kilowatts for car specs, metric PS to hp for European models, and watts to BTU/h for heating and air conditioning. Mechanical, metric and electrical horsepower are kept separate so results match the spec sheet.
Real-World Benchmarks
Multi-Unit Conversion Matrix
| Group | Measurement | Symbol | Equivalent Value |
|---|---|---|---|
| SI & Metric | Milliwatt | mW | 7.4570E7 |
| SI & Metric | Watt | W | 74,569.9872 |
| SI & Metric | Kilowatt | kW | 74.57 |
| SI & Metric | Megawatt | MW | 0.0746 |
| Horsepower | Mechanical Horsepower | hp | 100 |
| Horsepower | Metric Horsepower (PS) | PS | 101.387 |
| Horsepower | Electrical Horsepower | hp(E) | 99.9598 |
| Thermal & Imperial | BTU per Hour | BTU/h | 254,443.3578 |
| Thermal & Imperial | Foot-Pound per Second | ft·lbf/s | 55,000 |
| Thermal & Imperial | Kilocalorie per Hour | kcal/h | 64,118.6476 |
| Thermal & Imperial | Ton of Refrigeration | TR | 21.2036 |
Step-by-Step Mathematical Explanation
- Step 1: Convert 100 hp to the base unit (W): 100 × 745.699871582 = 74,569.987158 W.
- Step 2: Convert base watts to kilowatts: 74,569.987158 ÷ 1,000 = 74.569987 kW.
- Direct factor: 1 hp = 0.74569987 kW.
Essential Conversion Factors
Mechanical Horsepower: US & UK imperial horsepower (550 ft·lbf/s)
Quick Answer & Key Power Formulas
Direct Answer: To convert horsepower to kilowatts, multiply by 0.7457: kW = hp × 0.745700. To convert kilowatts to horsepower, multiply by 1.34102: hp = kW × 1.34102. Metric horsepower is slightly smaller: 1 PS = 0.7355 kW = 0.9863 hp. One kilowatt equals 3,412 BTU/h.
Understanding Power Units & Conversion Math
Power is the rate of doing work. James Watt defined one horsepower as 550 foot-pounds per second — exactly 745.69987 W. Continental Europe later adopted a metric horsepower (PS, CV, pk) of 75 kilogram-force meters per second, or 735.49875 W.
1. Horsepower to Kilowatts (hp → kW)
Multiply mechanical horsepower by 745.7 W and divide by 1,000 to get kilowatts:
Example: 300 hp × 0.7457 = 223.7 kW.
2. Kilowatts to Horsepower (kW → hp)
Divide kilowatts by 0.7457 — or multiply by the reciprocal, 1.34102:
Example: 150 kW × 1.34102 = 201.2 hp.
Mechanical hp vs Metric PS
A PS (Pferdestärke) is about 1.4% smaller than a mechanical horsepower, so a PS figure always looks slightly higher for the same engine:
A 150 PS European car = 147.9 hp = 110.3 kW.
Common Power Benchmarks
| Machine | Watts / kW | Horsepower | Significance |
|---|---|---|---|
| LED Light Bulb | 10 W | 0.013 hp | Replaces a 60 W incandescent |
| Human Cyclist | 200 W | 0.27 hp | Sustained amateur effort |
| E-Bike Motor | 250 W | 0.34 hp | EU legal limit for pedelecs |
| Microwave Oven | 1,000 W | 1.34 hp | Typical cooking output |
| Compact Car | 75 kW | 100.6 hp | Small petrol hatchback |
| Sports Car | 335.6 kW | 450 hp | Performance coupe |
| Wind Turbine | 3 MW | 4,023 hp | Modern onshore turbine |
Frequently Asked Questions
How many watts is 1 horsepower?
One mechanical horsepower equals 745.7 W (exactly 745.69987158 W). One metric horsepower (PS) equals 735.49875 W, and one electrical horsepower equals exactly 746 W.
What is the difference between hp, PS and bhp?
hp is mechanical horsepower (745.7 W) and PS is metric horsepower (735.5 W). bhp, or brake horsepower, is simply mechanical horsepower measured at the crankshaft before drivetrain losses.
Why do EU car documents list power in kW?
The kilowatt is the legal SI unit of power in the European Union, so registration documents (field P.2) show kW. Marketing materials usually add PS alongside it.
How do I convert BTU/h to watts?
Multiply BTU/h by 0.29307: a 12,000 BTU/h air conditioner is 3,517 W (3.5 kW) of cooling. One kilowatt equals 3,412 BTU/h.