How to use the power converter
- Type a number in the From box. 100 is entered for you, and decimals and commas both work, such as 2.5 or 36,000.
- Pick the unit you have in the first menu and the unit you want in the second. The To box and the result line update as you type.
- To work backwards, type in the To box instead.
- Press Swap units to flip the direction, or read The same power in other units for every unit at once.
How the conversion works
Every unit is stored as a size in watts, and the tool computes result = value × From size ÷ To size. The sizes come from the definitions, not rounded shortcuts. A mechanical horsepower is 550 foot-pounds of force per second, exactly 745.69987 W. A metric horsepower (PS) is 75 kgf·m/s, exactly 735.49875 W, and electrical horsepower is fixed at 746 W. A BTU per hour (International Table BTU) is 0.29307107 W, and a ton of refrigeration is 12,000 BTU/h, or 3,516.8528 W. These match NIST Guide to the SI, Appendix B.8. Answers show up to 8 significant digits.
Worked example with the default values
With 100 in the From box, Kilowatt (kW) as the From unit and Mechanical horsepower (hp) as the To unit, the result line reads 100 kW = 134.10221 hp, because 100,000 W ÷ 745.69987 W = 134.10221. The reverse line reads 1 hp = 0.74569987 kW, and the grid adds 135.96216 PS and 341,214.16 BTU/h.
Horsepower to kilowatts
| Mechanical | In kW | Metric | In kW |
|---|---|---|---|
| 1 hp | 0.7457 kW | 1 PS | 0.7355 kW |
| 10 hp | 7.457 kW | 10 PS | 7.355 kW |
| 100 hp | 74.57 kW | 100 PS | 73.55 kW |
| 150 hp | 111.85 kW | 150 PS | 110.32 kW |
| 200 hp | 149.14 kW | 200 PS | 147.1 kW |
| 300 hp | 223.71 kW | 300 PS | 220.65 kW |
Air conditioner tons, BTU/h and kW
| Size | Cooling in BTU/h | Cooling in kW |
|---|---|---|
| 1 ton | 12,000 BTU/h | 3.5169 kW |
| 2 ton | 24,000 BTU/h | 7.0337 kW |
| 3 ton | 36,000 BTU/h | 10.551 kW |
| 4 ton | 48,000 BTU/h | 14.067 kW |
| 5 ton | 60,000 BTU/h | 17.584 kW |
These are cooling outputs, not electricity drawn. To size a room, use the BTU calculator, and to price the electricity, use the electricity cost calculator. For kWh and joules, try the energy converter, and for engine output from torque and RPM, the horsepower and torque calculator.
Limits and edge cases
Negative values convert normally, for example power flowing backwards. Letters, currency symbols and slashes are blocked with a hint, and numbers above 1,000,000,000,000,000,000,000,000 are refused. BTU means the International Table BTU (the thermochemical BTU is about 0.07% smaller), and kcal/h uses the 4.1868 J calorie. A ton of refrigeration is a cooling rate, not a weight. Boiler horsepower is not included.
Sources: NIST Guide to the SI, Appendix B.8.
Power Converter FAQ
How many watts are in a horsepower?
One mechanical (US) horsepower is 745.7 watts. One metric horsepower (PS) is 735.5 watts and one electrical horsepower is exactly 746 watts, so the three differ by at most about 1.4%.
How do I convert kW to hp?
Multiply kilowatts by 1.341 for mechanical horsepower, so 100 kW is 134.10221 hp. For metric horsepower (PS), multiply by 1.35962 instead.
How many BTU/h is a 1 ton air conditioner?
One ton of cooling is 12,000 BTU/h, which equals 3.5169 kW. The name comes from the heat needed to melt one short ton (2,000 lb) of ice in 24 hours, which is 288,000 BTU.
Is a 36,000 BTU/h air conditioner a 10.55 kW unit?
Only as cooling. 36,000 BTU/h is 10.551 kW of heat removed, but an air conditioner moves heat instead of making it. A 3 ton unit with a SEER rating of 12 to 16 draws roughly 2.3 to 3 kW of electricity.
What is the difference between hp and PS?
PS (Pferdestärke) is the metric horsepower, 735.49875 W. The mechanical horsepower used in the US is 745.69987 W, about 1.4% larger, so 150 hp is slightly more power than 150 PS.