Power Converter

Convert between different power units including watts, kilowatts, horsepower, BTU/hr, and more.

Transform power measurements between various units used in electrical engineering, mechanical systems, and energy calculations. Supports common units like watts, kilowatts, horsepower, and BTU per hour.

Examples

Click on any example to load it into the converter.

Electrical Motor (Watts to Horsepower)

Electrical

Convert a 1500-watt electric motor to horsepower for mechanical applications.

Power Value: 1500

From Unit: Watts (W)

To Unit: Horsepower (hp)

Industrial Pump (Kilowatts to BTU/hr)

Industrial

Convert a 75-kilowatt industrial pump to BTU per hour for HVAC calculations.

Power Value: 75

From Unit: Kilowatts (kW)

To Unit: BTU per Hour (BTU/hr)

Car Engine (Horsepower to Kilowatts)

Automotive

Convert a 200-horsepower car engine to kilowatts for international specifications.

Power Value: 200

From Unit: Horsepower (hp)

To Unit: Kilowatts (kW)

Heating System (BTU/hr to Watts)

Heating

Convert a 50,000 BTU/hr heating system to watts for electrical planning.

Power Value: 50000

From Unit: BTU per Hour (BTU/hr)

To Unit: Watts (W)

Other Titles
Understanding Power Converter: A Comprehensive Guide
Master the art of power unit conversion across electrical, mechanical, and thermal systems. Learn the fundamental relationships between different power units and their practical applications in engineering and energy management.

What is Power and Why Convert Between Units?

  • Fundamental Concepts of Power
  • Historical Development of Power Units
  • Global Standardization Needs
Power is the rate at which work is done or energy is transferred. It represents how quickly energy is being used, generated, or converted from one form to another. The fundamental unit of power in the International System of Units (SI) is the watt (W), defined as one joule per second. However, different industries and regions have developed their own preferred units based on historical practices, practical applications, and measurement convenience.
The Evolution of Power Measurement Systems
The watt was named after James Watt, the Scottish engineer who improved the steam engine and established horsepower as a unit of power measurement. Horsepower was originally defined as the power needed to lift 550 pounds one foot in one second, making it practical for mechanical applications. The British Thermal Unit (BTU) emerged from heating and cooling applications, representing the energy needed to raise one pound of water by one degree Fahrenheit. These historical units remain relevant today alongside modern SI units.
The Need for Unit Conversion in Modern Engineering
In today's globalized engineering environment, professionals regularly encounter power specifications in different units. Electrical engineers work with watts and kilowatts, mechanical engineers use horsepower, HVAC technicians rely on BTU/hr, and international projects require conversion between metric and imperial systems. Accurate power conversion is essential for system design, equipment selection, energy efficiency analysis, and regulatory compliance across diverse applications.
Common Power Units and Their Applications
Watts (W) are the standard unit for electrical power, commonly used for small appliances and electronic devices. Kilowatts (kW) represent larger electrical systems like motors, generators, and industrial equipment. Horsepower (hp) remains popular in automotive, mechanical, and pump applications. BTU per hour (BTU/hr) is standard in heating, ventilation, and air conditioning systems. Megawatts (MW) are used for large-scale power generation and transmission systems.

Power Unit Applications:

  • Watts: LED light bulbs (5-100W), phone chargers (5-25W), small electronics
  • Kilowatts: Household appliances (1-5kW), electric motors (10-100kW), solar panels
  • Horsepower: Car engines (100-500hp), pumps (1-50hp), industrial machinery
  • BTU/hr: Air conditioners (5,000-60,000 BTU/hr), furnaces (40,000-200,000 BTU/hr)

Step-by-Step Guide to Using the Power Converter

  • Input Preparation and Validation
  • Conversion Process and Accuracy
  • Result Interpretation and Verification
Effective power conversion requires systematic approach to ensure accuracy and meaningful results. Follow this comprehensive methodology to convert power units correctly and interpret the results appropriately for your specific application.
1. Understanding Your Power Value and Context
Begin by clearly identifying the power value you need to convert. Determine whether this represents electrical power (watts, kilowatts), mechanical power (horsepower), or thermal power (BTU/hr). Consider the context of your application—is this for equipment specification, energy efficiency analysis, system design, or regulatory reporting? Understanding the source and intended use of the power value helps ensure you select appropriate units and interpret results correctly.
2. Selecting Appropriate Source and Target Units
Choose your source unit based on the original measurement or specification. For electrical systems, typically use watts or kilowatts. For mechanical systems, horsepower is common. For heating/cooling applications, BTU/hr is standard. Select your target unit based on your application requirements, industry standards, or regulatory requirements. Consider whether you need precision (use smaller units like watts) or convenience (use larger units like kilowatts or megawatts) for your specific use case.
3. Performing the Conversion with Precision
Enter your power value accurately, ensuring you use the correct decimal places and significant figures. Double-check that your source and target units are different to avoid unnecessary conversions. The converter will apply the appropriate conversion factors based on established relationships between units. For example, 1 horsepower equals 745.7 watts, 1 kilowatt equals 1,000 watts, and 1 BTU/hr equals 0.293 watts. These conversion factors are based on international standards and are precise for engineering applications.
4. Verifying and Applying Your Results
Review your converted value for reasonableness. Does the result make sense for your application? For example, a 100-watt light bulb should convert to approximately 0.134 horsepower, which is reasonable for a small mechanical system. Consider the precision needed for your application—engineering calculations often require 3-4 significant figures, while general estimates may only need 1-2. Document both the original and converted values for future reference and verification.

Conversion Accuracy Guidelines:

  • Electrical to Mechanical: 1 kW = 1.341 hp (standard conversion factor)
  • Electrical to Thermal: 1 kW = 3,412 BTU/hr (exact conversion)
  • Mechanical to Electrical: 1 hp = 745.7 W (standard conversion factor)
  • Precision Requirements: Use 3-4 significant figures for engineering calculations

Real-World Applications and Industry Standards

  • Electrical Engineering and Power Systems
  • Mechanical Engineering and Automotive
  • HVAC and Building Systems
Power conversion plays a critical role across diverse engineering disciplines and industries, enabling effective communication, system design, and performance analysis. Understanding industry-specific unit preferences and conversion requirements is essential for professional practice and successful project execution.
Electrical Engineering and Power Distribution
Electrical engineers primarily work with watts, kilowatts, and megawatts for power system design, load calculations, and energy efficiency analysis. Power conversion is essential when integrating equipment from different manufacturers or regions. For example, European motors may be rated in kilowatts while American electrical codes reference horsepower. Power factor corrections, transformer sizing, and generator selection all require accurate power unit conversions. Renewable energy systems often require conversion between DC power (watts) and AC power (volt-amperes) for grid integration.
Mechanical Engineering and Automotive Applications
Mechanical engineers and automotive professionals rely heavily on horsepower for engine specifications, pump sizing, and mechanical system design. However, international markets and regulations often require kilowatt ratings. Power conversion is crucial for vehicle specifications, engine performance analysis, and compliance with emissions standards. Pump and compressor selection requires conversion between mechanical horsepower and electrical kilowatts for motor sizing. Hydraulic and pneumatic systems often use different power units that must be converted for system integration.
HVAC and Building Energy Management
Heating, ventilation, and air conditioning systems use BTU/hr as the standard unit for thermal power, while electrical components are rated in watts or kilowatts. Power conversion enables integrated system design, energy efficiency calculations, and cost analysis. Building energy codes often specify requirements in different units that must be converted for compliance verification. Heat pump efficiency calculations require conversion between electrical input power (watts) and thermal output power (BTU/hr) to determine coefficient of performance (COP).

Industry-Specific Conversion Requirements:

  • Automotive: Engine power in hp, electrical systems in kW, emissions in g/kWh
  • HVAC: Cooling capacity in BTU/hr, electrical consumption in kW, efficiency in COP
  • Renewable Energy: Solar panels in W, inverters in kW, grid capacity in MW
  • Industrial: Motors in hp, generators in kW, process heat in BTU/hr

Common Misconceptions and Conversion Pitfalls

  • Unit Confusion and Naming Conventions
  • Precision and Significant Figures
  • Context and Application Errors
Power conversion errors can lead to significant design problems, equipment mismatches, and safety issues. Understanding common misconceptions and avoiding typical pitfalls is essential for accurate engineering calculations and reliable system performance.
Myth: All Power Units Are Interchangeable Without Loss
This misconception leads to oversimplified conversions that ignore important context and precision requirements. Reality: Different power units have specific applications and precision characteristics. For example, converting 1,000 watts to 1.341 horsepower loses precision that may be critical for mechanical system design. Some conversions involve efficiency factors that vary with operating conditions. Electrical power (watts) and apparent power (volt-amperes) are fundamentally different concepts that cannot be directly converted without considering power factor.
Precision and Significant Figure Management
Power conversion often involves numbers with many decimal places, leading to precision errors. Engineers must maintain appropriate significant figures throughout calculations. For example, converting 100 horsepower to watts gives 74,570 watts, but maintaining 74,600 watts (3 significant figures) may be more appropriate for most applications. Rounding errors can accumulate in complex calculations, so it's essential to carry extra precision during intermediate steps and round only at the final result.
Context and Application-Specific Considerations
Power conversion must consider the specific application context. For example, automotive horsepower ratings (SAE) differ from mechanical horsepower (metric) by about 1.4%. Electrical horsepower (746 watts) differs from mechanical horsepower (745.7 watts) due to efficiency considerations. Thermal power in BTU/hr may need adjustment for different temperature conditions. Understanding these context-specific factors prevents conversion errors that could affect system performance or safety.

Common Conversion Errors:

  • Confusing power (watts) with energy (watt-hours) in time-based calculations
  • Using rounded conversion factors (1 hp = 750 W) instead of precise values (745.7 W)
  • Ignoring power factor in electrical to mechanical power conversions
  • Applying thermal efficiency factors incorrectly in heat-to-work conversions

Mathematical Derivation and Conversion Factors

  • Fundamental Power Relationships
  • Conversion Factor Development
  • Precision and Uncertainty Analysis
Understanding the mathematical foundation of power conversion enables accurate calculations and helps identify potential sources of error. The relationships between different power units are based on fundamental physical principles and international standards that ensure consistency across applications and regions.
Fundamental Power Definitions and Relationships
Power is fundamentally defined as the rate of energy transfer or work done per unit time. In SI units, 1 watt equals 1 joule per second. This relationship provides the foundation for all power conversions. Mechanical power relates force, distance, and time: P = F × d/t. Electrical power relates voltage, current, and time: P = V × I. Thermal power relates heat transfer and time: P = Q/t. These fundamental relationships enable conversion between different power measurement systems.
Development of Standard Conversion Factors
Standard conversion factors are established through precise measurements and international agreements. The horsepower-to-watt conversion (1 hp = 745.7 W) is based on the mechanical definition of 550 foot-pounds per second. The BTU/hr-to-watt conversion (1 BTU/hr = 0.293 W) is based on the thermal energy required to raise one pound of water by one degree Fahrenheit. These factors are maintained by international standards organizations to ensure consistency in engineering calculations worldwide.
Precision and Uncertainty in Power Conversion
Power conversion involves inherent uncertainties that must be considered in engineering applications. Conversion factors have associated uncertainties, typically less than 0.1% for standard units. Measurement uncertainties in the original power values can be magnified through conversion. For critical applications, engineers should use conversion factors with appropriate precision and document uncertainty sources. Statistical methods can be applied to estimate the combined uncertainty of converted power values.

Mathematical Relationships:

  • 1 W = 1 J/s (fundamental SI definition)
  • 1 hp = 550 ft·lb/s = 745.7 W (mechanical definition)
  • 1 BTU/hr = 0.293 W (thermal definition)
  • 1 kW = 1,000 W (metric prefix relationship)