Power Converter

Power is the rate at which energy is transferred or converted, measured as energy per unit time. In physics, power quantifies how quickly work is done or energy is consumed. The SI unit of power is the watt (W), defined as one joule per second (1 W = 1 J/s). Power is fundamental to understanding electrical systems, mechanical engines, heating and cooling systems, and virtually every aspect of modern technology.

Different industries and applications use different power units. The kilowatt (kW) is standard for household electricity, appliances, and small motors. The megawatt (MW) is used for power plants and large industrial systems. Horsepower (HP) remains the standard for automotive engines and motors in the US, while metric horsepower (PS) is used in Europe. The BTU per hour (BTU/hr) is the standard for heating and cooling systems in the US. The foot-pound per second (ft-lb/s) is used in mechanical engineering, and the calorie per second (cal/s) and kilocalorie per hour (kcal/hr) appear in thermodynamics and nutrition contexts.

The concept of power is distinct from energy. Energy (measured in joules, kilowatt-hours, or BTU) represents the total amount of work done, while power represents how fast that work occurs. A 100-watt light bulb consumes 100 joules of energy per second. A 100-kW motor can do work 1,000 times faster than a 100-W bulb. Understanding this distinction is essential for sizing electrical circuits, engines, and heating systems correctly.

Power conversion is essential when comparing specifications across different industries, international standards, and measurement systems. Engineers, technicians, and consumers all benefit from understanding how different power units relate to one another.

All power conversions in this calculator are based on exact or highly precise conversion factors that relate each unit to the watt, the SI unit of power.

The key conversion factors are: 1 kW = 1000 W (exact), 1 MW = 1,000,000 W (exact), 1 HP (mechanical) = 745.7 W (exact by definition), 1 PS (metric HP) = 735.49875 W (exact), 1 BTU/hr = 0.29307107 W (exact), 1 ft-lb/s = 1.3558179 W (exact), 1 cal/s = 4.184 W (exact, since 1 cal = 4.184 J), and 1 kcal/hr = 1.163 W (exact).

The conversion method works by first converting the input value to watts using the from-unit's factor, then converting from watts to the target unit using the to-unit's factor: result = (value × fromFactor) / toFactor. This two-step approach through watts ensures accuracy regardless of which two units are being converted.

The distinction between mechanical horsepower (HP = 745.7 W) and metric horsepower (PS = 735.5 W) is important. Mechanical HP is defined as exactly 550 foot-pounds per second, while metric PS is defined as the power needed to raise 75 kg by 1 meter in 1 second. The difference (about 1.4%) is small but significant in precise engineering calculations.

This power converter supports nine different power units with a bidirectional conversion interface:

1. Enter the Value: Type the numerical value into the input field.
2. Select the From Unit: Choose the source power unit from the dropdown (e.g., kilowatts, horsepower, BTU/hr).
3. Select the To Unit: Choose the target power unit from the second dropdown.
4. Swap Units: Use the swap button (↔) to quickly reverse the conversion direction.
5. View the Result: The main display shows the converted value with the target unit label.
6. Review All Conversions: The "All Conversions" panel shows the input value expressed in every supported unit simultaneously, making it easy to compare across all power scales.

The converter displays the input value expressed in all nine supported power units. This comprehensive view helps you understand the relative magnitude of different power measurements and choose the most appropriate unit for your context.

For reference, common power levels provide useful benchmarks. A typical household circuit in the US handles 1,800 W (1.8 kW). A standard microwave oven operates at about 1,000 W (1 kW). A car engine typically produces 100–300 HP (75–225 kW). A large power plant generates 500–2,000 MW. A human at rest generates about 80 W of metabolic power, while a professional cyclist can sustain 400 W for extended periods.

The Quick Reference panel provides the most commonly needed conversion factors: 1 HP = 745.7 W, 1 kW = 1.34 HP, 1 BTU/hr = 0.293 W, and 1 metric HP (PS) = 735.5 W. These values are essential for quickly converting between the units most commonly encountered in automotive, electrical, and HVAC applications.

Power conversion is critical in automotive engineering, where engine output is measured in horsepower (HP) in the US and kilowatts (kW) or PS in Europe and Asia. A car rated at 200 HP has an engine producing approximately 149 kW. European car specifications list power in kW, so converting between HP and kW is essential when comparing vehicles across markets. Electric vehicle motors are typically rated in kW, making this conversion increasingly relevant as EVs become mainstream.

In electrical engineering and home improvement, power ratings determine circuit sizing, generator capacity, and appliance efficiency. A 3-ton air conditioner uses about 3,500 W (3.5 kW), while a portable generator might be rated at 7,500 W (7.5 kW) or 10,000 BTU/hr for heating capacity. Converting between watts, kilowatts, and BTU/hr is essential for selecting appropriately sized equipment and ensuring electrical safety.

HVAC (Heating, Ventilation, and Air Conditioning) professionals routinely convert between BTU/hr and watts. A standard residential furnace might be rated at 80,000 BTU/hr, which equals approximately 23.4 kW. Heat pump specifications often list both BTU/hr and kW ratings. Understanding these conversions helps HVAC technicians size equipment correctly for the space being heated or cooled.

In industrial and power generation contexts, megawatts (MW) and gigawatts (GW) are the standard units. A typical coal-fired power plant generates 500–1,000 MW, while a nuclear power plant produces 1,000–4,000 MW. Wind turbines are rated in megawatts, with modern offshore turbines producing 10–15 MW each. These large-scale power measurements require familiarity with the full range of power units.