Convert power quantities instantly across Watts, kW, MW, Mechanical Horsepower, Metric PS, Electrical HP, BTU/h, and ft-lbf/s with exact NIST coefficients.
Engineering & Industrial Power Milestones
🎯 Estimate-First Engineering Challenge
Before checking below, can you estimate how many Mechanical Horsepower (hp) equal 100 kW?
Target (Mechanical Horsepower)
134.102209
Equivalent Electrical Current Draw
833.33 A @ 120V
434.78 A @ 230V
Single-phase resistive mains amperage (US vs EU/Asia)
Logarithmic Magnitude (Watts)100,000 W
1 W100 W10 kW1 MW10 MW
Simultaneous 8-Unit Equivalency Matrix
Watts (W)
100,000
Kilowatts (kW)
100
Megawatts (MW)
0.1
Mechanical Horsepower (hp)
134.10221
Metric Horsepower (PS/cv)
135.96216
Electrical Horsepower (hp(E))
134.04826
BTU per Hour (BTU/h)
341,214.16331
Foot-Pounds / Sec (ft-lbf/s)
73,756.21493
Step-by-Step Mathematical Walkthrough
Step 1: Convert source unit to base SI Watts (W)
Watts = 100 kW × 1,000 = 100,000 W
Step 2: Convert Watts to target unit (Mechanical Horsepower)
Mechanical Horsepower = 100,000 W / 745.699871582 = 134.102209 hp
Step 3: Equivalent Single-Phase Electrical Current Draw (Amps)
I (120V US) = 100,000 W / 120 V = 833.3333 A | I (230V EU/Asia) = 100,000 W / 230 V = 434.7826 A
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About the Power Converter
Power is the rate at which energy is transferred or converted, and it is one of the most frequently misunderstood quantities in everyday engineering because it is so often confused with energy itself. The SI unit is the watt, defined as one joule per second. Around it sits a collection of legacy and trade-specific units: three different definitions of horsepower, the BTU per hour used throughout heating and air-conditioning, and the foot-pound per second from which mechanical horsepower was originally derived. The confusion is compounded by units that measure energy rather than power, such as the kilowatt-hour on an electricity bill, and by the refrigeration ton used to rate air conditioners. Converting between these correctly matters when comparing an engine specified in horsepower with a motor rated in kilowatts, or when sizing an air conditioner quoted in BTU per hour against a generator rated in kilowatts.
Mathematical Formula & Logic
Power is energy per unit time, converted through a common base of watts.
1. Definition:
P = E / t = W / t
1 watt (W) = 1 joule per second = 1 kg·m²·s⁻³
For mechanical rotation: P = τ × ω (torque × angular velocity)
For electrical circuits: P = V × I (voltage × current)
2. Conversion method:
value_in_watts = input × factor(from_unit)
result = value_in_watts ÷ factor(to_unit)
3. Conversion factors to watts:
1 kW = 1,000 W (exact, SI prefix)
1 MW = 1,000,000 W (exact, SI prefix)
1 hp (mech) = 745.6998715822702 W (= 550 ft·lbf/s exactly)
1 PS (metric) = 735.49875 W (= 75 kgf·m/s exactly)
1 hp (elec) = 746 W (exact by convention)
1 BTU/h ≈ 0.2930710701722222 W
1 ft·lbf/s = 745.6998715822702 / 550 W
4. Power versus energy — the critical distinction:
Energy = Power × Time
A 1,000 W appliance running for 1 hour consumes 1 kWh of energy.
The watt is a rate; the kilowatt-hour is a quantity.
Step-by-Step Example
Convert a car engine rated at 150 mechanical horsepower into kilowatts and metric horsepower:
1. Identify the source factor: 1 hp (mechanical) = 745.6998715822702 W.
2. Convert the input to the base unit:
150 × 745.6998715822702 = 111,854.98 W
3. Convert watts to kilowatts by dividing by 1,000:
111,854.98 ÷ 1,000 = 111.85 kW
4. Convert watts to metric horsepower by dividing by 735.49875:
111,854.98 ÷ 735.49875 = 152.08 PS
5. Result: 150 hp = 111.85 kW = 152.08 PS.
This is why the same engine is advertised as 150 hp in the United Kingdom and roughly 152 PS in Germany. The car has not changed; only the definition of horsepower has. Metric horsepower is about 1.4 percent smaller than mechanical horsepower, so the PS figure is always slightly the larger number.
Reference Data & Values
unit
watts
typical use
Watt (W)
1
SI unit; LED bulbs, small electronics
Kilowatt (kW)
1,000
Motors, EV charging, appliances
Megawatt (MW)
1,000,000
Power stations, grid capacity
Mechanical horsepower (hp)
745.69987
US and UK engine ratings
Metric horsepower (PS/cv)
735.49875
European and Japanese engine ratings
Electrical horsepower
746
Electric motor nameplates
BTU per hour
0.29307107
Heating and air-conditioning capacity
Foot-pound per second
1.35582
Imperial mechanics; origin of hp
Frequently Asked Questions
Each was defined by a different trade for a different purpose and none was ever retired. Mechanical horsepower, at 550 foot-pounds per second or about 745.7 watts, came from James Watt’s estimate of what a dray horse could sustain while turning a mill wheel. Metric horsepower was defined independently in continental Europe as 75 kilogram-force metres per second, or exactly 735.49875 watts, making it roughly 1.4 percent smaller. Electrical horsepower was rounded to a flat 746 watts for motor nameplates. The differences are small enough to ignore casually and large enough to matter in a specification.
A kilowatt is a rate of energy flow, while a kilowatt-hour is a quantity of energy delivered. The relationship is Energy = Power × Time, so a 2 kW heater running for three hours consumes 6 kWh. Your electricity meter bills kilowatt-hours because it charges for total energy consumed, whereas an appliance nameplate states kilowatts because it describes how fast that appliance draws energy. Confusing the two is the single most common error in home energy calculations.
One BTU per hour is approximately 0.29307 watts, so a 12,000 BTU/h air conditioner has a cooling capacity of about 3,517 watts, or 3.52 kilowatts. That 12,000 BTU/h figure is also called one ton of refrigeration, a unit that dates from the rate of cooling produced by melting one short ton of ice over twenty-four hours. Note that cooling capacity is not the same as electrical consumption: an efficient unit delivering 3.5 kW of cooling might draw only about 1 kW from the wall.
Kilowatts are the engineering unit that electrical systems, batteries and charging infrastructure are actually specified in, while horsepower remains the figure buyers have decades of intuition about. Manufacturers publish both so that a 150 kW motor can be understood as roughly 201 mechanical horsepower by someone comparing it against a petrol car. The same dual labelling appears on charging speeds, where a 150 kW charger describes energy delivery rate rather than motor output.
Power equals torque multiplied by angular velocity, so in SI units P = τ × 2πN/60, where torque is in newton-metres and N is revolutions per minute. An engine producing 300 N·m at 4,000 rpm therefore delivers 300 × 2π × 4000 / 60 ≈ 125,664 watts, or about 126 kW. This is why peak power and peak torque occur at different engine speeds: power is the product of the two, so it keeps climbing after torque has begun to fall.
Usually no. A nameplate watt rating is generally the maximum rated draw under full load, not a constant figure. A refrigerator compressor cycles on and off, so its average consumption over a day is far below its nameplate value, and a laptop charger rated at 65 W draws that only while the battery is charging hard. For energy cost estimates you need actual consumption over time in kilowatt-hours, which is why a plug-in energy monitor gives more useful numbers than the label.