Power converter — watts, kilowatts and horsepower

Engine outputs, appliance ratings, solar arrays and air-conditioning capacities — eight power units, including both kinds of horsepower that manufacturers quietly swap between.

How to use it

1
Type into any row — say kW or hp. The results appear immediately, no button needed.
2
Need a combined figure? Fill in two rows, for example kW and W, and they are added together before converting.
3
Set how many digits you want (4–12) and click a result to copy the plain number.

Exact conversion factors

These are the definitions the calculator uses. Nothing here is rounded for convenience — where a value is exact by definition, it says so.

1 hp (mechanical) = 745.69987158 W · 1 PS (metric) = 735.49875 W
1 kW = 1.34102209 hp = 1.35962162 PS
1 hp = 1.01386967 PS — a 1.4 percent gap
1 kW = 3412.14163 BTU/h · 12 000 BTU/h = 3.51685 kW

FormulaW = hp × 745.69987158 · W = PS × 735.49875 · kW = BTU/h × 0.00029307107

Power conversion table — every unit

One of each unit, converted into the three units people ask for most.

Unit	kW	hp	W
1 GW	1 000 000 kW	1 341 020 hp	1 000 000 000 W
1 MW	1 000 kW	1 341.02 hp	1 000 000 W
1 kW	1 kW	1.34102 hp	1 000 W
1 W	0.001 kW	0.00134102 hp	1 W
1 mW	0.000001 kW	0.00000134102 hp	0.001 W
1 hp	0.7457 kW	1 hp	745.7 W
1 PS	0.735499 kW	0.98632 hp	735.499 W
1 BTU/h	0.000293071 kW	0.000393015 hp	0.293071 W

kW → hp, W — quick values

kW	hp	W
0.5 kW	0.670511 hp	500 W
1 kW	1.34102 hp	1 000 W
2 kW	2.68204 hp	2 000 W
3 kW	4.02307 hp	3 000 W
5 kW	6.70511 hp	5 000 W
10 kW	13.4102 hp	10 000 W
20 kW	26.8204 hp	20 000 W
25 kW	33.5256 hp	25 000 W
50 kW	67.0511 hp	50 000 W
100 kW	134.102 hp	100 000 W
250 kW	335.256 hp	250 000 W
1 000 kW	1 341.02 hp	1 000 000 W

How this converter works

There are two horsepowers in common use and they differ by about 1.4 percent. Mechanical horsepower (hp) is 745.7 W and appears in British and American figures; metric horsepower (PS, ch, pk) is 735.5 W and is what most European manufacturers quote. A car sold as 150 PS is 148 hp — the same engine, a different yardstick.

BTU per hour is included for climate equipment, where a "12 000 BTU" unit means 12 000 BTU/h, or 3.52 kW of cooling. Reading it as energy rather than power is a common and expensive mistake in quotes.

Notes and abbreviations

1 hp (mechanical) = 745.70 W; 1 PS (metric) = 735.50 W
1 kW = 1.341 hp = 1.360 PS
BTU/h ratings on air conditioners are power, not energy

Questions

How many kW is 200 hp?

149.14 kW using mechanical horsepower, or 147.10 kW if the figure was quoted in metric PS.

Which horsepower does my car use?

European and Japanese brochures usually quote PS, UK and US ones hp. A round metric number is a good sign it is PS.

What size air conditioner is 3.5 kW?

11 942 BTU/h, sold as a 12 000 BTU unit.