Power Conversion Calculator — W, kW, hp, BTU/h, PS
Enter a power value and unit — get all conversions to watts, kilowatts, megawatts, mechanical and metric horsepower, BTU/h, ft-lbf/s and more simultaneously.
From unit
Equivalent power in watts — the SI base unit of power
- 1
Conversion factor
1 kW = 1,000 W = 1,000Number of watts in one unit of the selected source unit. - 2
Power in watts
1 × 1,000 = 1,000
How does this calculator work?
P_target = P_source × (source_factor / target_factor). 1 kW = 1000 W = 1.341 hp (mech.) = 1.360 PS (metric) = 3412 BTU/h. Enter your power value and unit to get all conversions simultaneously.
Formula
How this is calculated
Power is the rate of energy transfer, measured in watts (W) in the SI system — one watt equals one joule per second. Every other power unit is defined by a fixed conversion factor to watts: a kilowatt is exactly 1,000 W, a mechanical horsepower (as defined by the US National Bureau of Standards in 1959) is 745.699 871 6 W, a metric horsepower (PS, from the German Pferdestärke) is 735.498 75 W, and a BTU per hour is 0.293 071 W (one BTU ≈ 1055.06 J, divided by 3600 s).
The calculator first multiplies your input by the source factor to express it in watts, then divides by each target factor to produce all the other values simultaneously. Because all factors are exact physical definitions, the only precision loss comes from the floating-point representation of the constants — results are accurate to at least 10 significant figures.
Note: this tool converts instantaneous power (a rate, in watts or equivalents), not energy over time (in joules or watt-hours). Mechanical horsepower (used in the US for engines) and metric horsepower (common in European automotive specs) differ by about 1.4% — do not mix them when comparing engine ratings across countries.
Frequently asked questions
Mechanical (imperial) horsepower = 745.700 W; metric horsepower (PS) = 735.499 W — about 1.4% less. US vehicles are rated in mechanical hp; European vehicles often show PS or kW. The calculator shows both columns so you can compare directly.
Divide kilowatts by 0.7457 (or multiply by 1.3410) for mechanical hp. For example, 100 kW ≈ 134.1 hp (mechanical) or 136.0 PS (metric). Enter 100 kW in the calculator to see all conversions at once.
BTU/h measures thermal power — how fast a heating or cooling system moves heat. HVAC and air conditioning units in the US are commonly rated in BTU/h or tons of cooling (1 ton = 12,000 BTU/h = 3517 W). 1 BTU/h ≈ 0.293 W.
Also known as
TG we-Calculate Editorial Team. (2026). Power Conversion Calculator — W, kW, hp, BTU/h, PS [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/power-conversion-calculator
TG we-Calculate Editorial Team. "Power Conversion Calculator — W, kW, hp, BTU/h, PS." TG we-Calculate. 2026. https://we-calculate.com/calculator/power-conversion-calculator.
TG we-Calculate Editorial Team, "Power Conversion Calculator — W, kW, hp, BTU/h, PS," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/power-conversion-calculator
@misc{wecalculate_power_conversion_calculator, title = {Power Conversion Calculator — W, kW, hp, BTU/h, PS}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/power-conversion-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?