About this calculator
Type a number, choose the unit you have and the unit you want, and this converter gives you the answer at once, along with the same power in every other unit it knows.
Every conversion factor is exact by definition wherever one exists, and each result shows the working so you can check it.
Worked examples
Real numbers, worked out by the same calculator. Press “Use these numbers” to try one above.
1 hp to kW
- kilowatts (kW)
- 0.745699871582 kW
- watts (W)
- 745.699871582 W
- megawatts (MW)
- 0.00074569987158 MW
- metric horsepower (PS)
- 1.01386966542 PS
- BTU per hour (BTU/h)
- 2,544.43357764 BTU/h
- kilocalories per hour (kcal/h)
- 641.615568295 kcal/h
1 hp is 0.745699871582 kW.
Show the working
- Change to the base unit (W): 1 hp × 745.699871582 = 745.699871582 W.
- Change to kW: 745.699871582 ÷ 1,000 = 0.745699871582 kW.
100 kW to hp
- horsepower, mechanical (hp)
- 134.10220896 hp
- watts (W)
- 100,000 W
- megawatts (MW)
- 0.1 MW
- metric horsepower (PS)
- 135.96216173 PS
- BTU per hour (BTU/h)
- 341,214.163313 BTU/h
- kilocalories per hour (kcal/h)
- 86,042.0650112 kcal/h
100 kW is 134.10220896 hp.
Show the working
- Change to the base unit (W): 100 kW × 1,000 = 100,000 W.
- Change to hp: 100,000 ÷ 745.699871582 = 134.10220896 hp.
12,000 BTU/h to kW
- kilowatts (kW)
- 3.51685284207 kW
- watts (W)
- 3,516.85284207 W
- megawatts (MW)
- 0.00351685284207 MW
- horsepower, mechanical (hp)
- 4.71617734707 hp
- metric horsepower (PS)
- 4.78158914895 PS
- kilocalories per hour (kcal/h)
- 3,025.97280872 kcal/h
12,000 BTU/h is 3.51685284207 kW.
Show the working
- Change to the base unit (W): 12,000 BTU/h × 0.293071070172 = 3,516.85284207 W.
- Change to kW: 3,516.85284207 ÷ 1,000 = 3.51685284207 kW.
How to convert by hand
Every power unit is stored in watts (joules per second). Multiply by the size of the unit you have (in W), then divide by the size of the unit you want. For example, 150 hp × 745.69987 = 111,855 W, or 111.9 kW.
Conversion factors used
Each unit is stored as its size in W. The sizes below are the ones this converter uses.
| Unit | Size |
|---|---|
| watts (W) | 1 W |
| kilowatts (kW) | 1,000 W |
| megawatts (MW) | 1,000,000 W |
| horsepower, mechanical (hp) | 745.699871582 W |
| metric horsepower (PS) | 735.49875 W |
| BTU per hour (BTU/h) | 0.293071070172 W |
| kilocalories per hour (kcal/h) | 1.1622222222 W |
Common conversions
| From | To |
|---|---|
| 1 hp | 745.699871582 W |
| 1 PS | 735.49875 W |
| 100 hp | 74.5699871582 kW |
| 100 kW | 134.10220896 hp |
| 1 kW | 3,412.14163313 BTU/h |
| 1 MW | 1,000 kW |
| 1 BTU/h | 0.293071070172 W |
| 1,000 W | 1.3410220896 hp |
Horsepower is not one unit
The mechanical horsepower (used in the UK and US) is 745.7 W. The metric horsepower (PS, CV or pk, used in Europe) is exactly 735.49875 W. Car makers quote whichever they prefer, so a “150 hp” and a “150 PS” engine differ by about 1.4%.
Frequently asked questions
How many watts is one horsepower?
One mechanical horsepower is 745.7 watts.
How many kW is 100 hp?
100 mechanical horsepower is 74.57 kW.
What is BTU/h used for?
Heating and air-conditioning units are often rated in BTU per hour. 1 kW is about 3,412 BTU/h.
How accurate is this converter?
It uses the exact defined factors wherever they exist and shows up to 12 significant digits, so the results are accurate to far more digits than you will normally need.
Formulas tested against hand-worked answers. Last reviewed 29 September 2026. These calculators do arithmetic only; they are not financial, tax or legal advice.