Power Converter

W · kW · MW · hp · BTU/hr · kcal/hr · ft·lb/s

Convert power units instantly between metric and imperial systems. Supports watts, kilowatts, megawatts, horsepower, BTU/hr and more. Free online engineering tool.

1 unit =
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Key Formulas

  • 1 hp = 745.7 W
  • 1 kW = 1,000 W
  • 1 BTU/hr = 0.2931 W
Formula: 1 W = 1 W

Conversion Table

UnitNameValue

About Power Units

Power is the rate at which energy is transferred or converted — measured in watts (W) in the SI system. One watt equals one joule per second. In everyday life, power appears on appliance energy labels (watts or kilowatts), engine datasheets (horsepower or kW), and heating/cooling systems (BTU/hr or kcal/hr). Converting between these units is essential for engineers, electricians, and anyone comparing products across regions.

Horsepower (hp) remains the dominant unit for engine power in the US and UK, while kW is standard in Europe and for electric motors globally. BTU/hr (British Thermal Units per hour) is widely used for HVAC, air conditioners, and boilers in North America. Understanding these conversions helps you compare engine specs, size HVAC systems, calculate electricity bills, and design power systems accurately.

Quick Reference — Common Power Conversions

1 hp
745.7 W
= 0.7457 kW
1 kW
1,000 W
= 1.34102 hp
1 BTU/hr
0.29307 W
= 3.412 BTU/hr per W
1 MW
1,000 kW
= 1,341 hp
100 kW
134.1 hp
= 341,214 BTU/hr
1 ton (AC)
3,517 W
= 12,000 BTU/hr
1 kcal/hr
1.163 W
= 3.968 BTU/hr
1 ft·lb/s
1.3558 W
= 0.001818 hp
500 W
0.5 kW
= 0.671 hp
1 GW
1,000 MW
= 1,000,000 kW

Worked Examples

1 hp to watts

One mechanical horsepower is defined as exactly 550 foot-pounds per second, which equals 745.69987 watts.

1 hp = 745.7 W

5 kW to hp

Multiply kW by 1.34102. A 5 kW electric motor produces the same output as about 6.7 hp.

5 × 1.341 = 6.705 hp

1000 BTU/hr to watts

Multiply BTU/hr by 0.29307. Common for comparing HVAC systems between metric and imperial specs.

1000 × 0.29307 = 293.1 W

100 W to kcal/hr

Multiply watts by 0.8598. Useful for nutritional and metabolic power calculations.

100 × 0.8598 = 85.98 kcal/hr

Where Power Conversion Is Used

Electric Motors

Motor nameplates show kW in Europe and hp in North America. Converting is essential for selecting correct motor starters, cables and protection.

Home Appliances

Appliance labels show watts. Converting to kWh helps calculate running costs: a 2 kW heater running 4 hours uses 8 kWh of electricity.

Automotive Engines

Car specs list power in hp (US/UK) or kW (EU). A 200 hp engine produces 149.1 kW. Converting lets you compare models across markets.

HVAC Systems

Air conditioners are rated in BTU/hr (US) or kW (EU). A 12,000 BTU/hr (1 ton) unit equals 3.52 kW cooling capacity.

Solar Panels

Solar panels are rated in watts peak (Wp). A 400 W panel in 5 peak sun hours generates 2 kWh/day. Conversion helps size battery storage.

Data Centres

Server racks are rated in kW. Data centres measure total power in MW. Converting between W, kW and MW is routine for power budgeting.

Mental Math Tips

hp to watts

hp × 746 = watts
~0.75 kW per hp

kW to hp

kW × 1.341 = hp
~4/3 × kW

W to kW

W ÷ 1000 = kW
Move decimal 3 left

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Frequently Asked Questions

A watt (W) is the SI unit of power, defined as one joule per second (J/s). It measures the rate at which energy is transferred or converted. Named after Scottish engineer James Watt, it is the standard unit for rating electrical appliances, engines, and light sources.
Power is the rate of doing work or transferring energy, measured in watts (W). Energy is the total amount of work done or energy transferred over time, measured in joules (J) or kilowatt-hours (kWh). The relationship is: Energy = Power \u00d7 Time. A 1 kW device running for 1 hour uses 1 kWh of energy.
One mechanical horsepower (hp) equals exactly 745.7 watts. One metric horsepower (PS) equals 735.5 watts. These differ because they were defined independently. Most car engine specs use mechanical hp in the US and metric PS in Europe. Our converter uses mechanical horsepower.
To convert kilowatts to mechanical horsepower, multiply by 1.34102. For example, 100 kW \u00d7 1.34102 = 134.1 hp. To convert hp to kW, multiply by 0.7457. So a 200 hp engine produces about 149.1 kW.
BTU stands for British Thermal Unit, a unit of energy. BTU/hr is a power unit measuring how many BTUs are transferred per hour. One BTU/hr equals 0.2931 watts. Air conditioners and heating systems are often rated in BTU/hr in the US — a 12,000 BTU/hr (1 ton) AC equals about 3,517 watts.
An average UK home uses about 3,100 kWh per year, equivalent to an average power of about 350 W. A US home averages around 10,500 kWh/year, about 1,200 W average. Actual power draw varies greatly depending on appliances in use at any given moment.
To convert motor horsepower to kilowatts, multiply by 0.7457. A 5 hp motor produces 5 \u00d7 0.7457 = 3.73 kW of mechanical output. Note that the electrical input power is higher due to motor efficiency losses — most motors are 85–95% efficient.

All Power Conversions

Common
W → kWkW → WkW → hphp → kWW → hphp → WMW → WW → MW
Metric
W → kWkW → WkW → MWMW → kWW → MW
Mechanical
hp → WW → hphp → kWkW → hphp → MW