Loading Calculator...
Please wait a moment
Please wait a moment
Convert between watts, kilowatts, horsepower, BTU/hour, and more instantly. Enter a value and see all power unit conversions in real-time.
| Unit | Symbol | Watts Equivalent |
|---|---|---|
| Watt | W | 1 W |
| Kilowatt | kW | 1,000 W |
| Megawatt | MW | 1,000,000 W |
| Horsepower (Mechanical) | hp | 745.7 W |
| Horsepower (Metric) | PS | 735.5 W |
| BTU per Hour | BTU/h | 0.293071 W |
| Calorie per Second | cal/s | 4.184 W |
| Joule per Second | J/s | 1 W (by definition) |
1 W = 0.001 kW
1 kW = 1,000 W
1 W = 0.000001 MW
1 MW = 1,000,000 W
1 W = 0.00134102 hp
1 hp = 745.7 W
1 W = 0.00135962 PS
1 PS = 735.5 W
1 W = 3.41214 BTU/h
1 BTU/h = 0.293071 W
1 W = 0.238846 cal/s
1 cal/s = 4.184 W
The watt (W) is the International System of Units (SI) base unit of power. One watt equals one joule of energy transferred per second (W = J/s). Named after Scottish inventor James Watt, this unit provides the universal standard for measuring power across all disciplines - electrical, mechanical, thermal, and more. Watts are used for everything from light bulbs to power plants.
Kilowatts (kW) and megawatts (MW) are metric prefixes applied to watts for convenience when dealing with larger power values. One kilowatt equals 1,000 watts, typically used for household appliances and small motors. One megawatt equals 1,000,000 watts, used for industrial facilities and power generation. These units make it easier to express and compare larger power ratings without unwieldy numbers.
Horsepower comes in different varieties. Mechanical horsepower (745.7 W), used primarily in North America, was defined by James Watt to compare steam engines to horses. Metric horsepower or PS (Pferdestärke, 735.5 W), used in Europe and Asia, is slightly smaller and based on the metric system. While both measure the same thing - mechanical power - the difference matters for precise engineering calculations and international equipment comparisons.
British Thermal Units per hour (BTU/h) measure the rate of heat energy transfer, commonly used for rating heating and cooling systems in the United States. One BTU/h equals approximately 0.293 watts. While not an SI unit, BTU/h remains the standard for residential and commercial HVAC equipment specifications. Understanding the watt equivalent helps compare HVAC systems internationally and calculate electrical power consumption.
Calories per second (cal/s) measure power in terms of heat generation rate, occasionally used in thermodynamics and food science contexts. One calorie per second equals 4.184 watts. This unit helps bridge mechanical and thermal power measurements, useful when analyzing energy conversion efficiency or metabolic processes.
Joules per second (J/s) is actually the definition of a watt - they are identical units (1 W = 1 J/s). Including J/s in power conversions emphasizes the relationship between power and energy: power is the rate of energy transfer. This helps understand that a 100 W light bulb consumes 100 joules of energy every second.
Use watts (W) for general purposes and small devices, kilowatts (kW) for appliances and home systems, megawatts (MW) for industrial and utility-scale power, horsepower (hp) for motors and engines, and BTU/h for HVAC systems. This converter lets you work in any unit and see equivalents in all others.
Power (watts) measures the rate of energy use at any instant - how fast energy is consumed or produced. Energy (watt-hours, joules) measures the total amount consumed over time. A 1,000 W (1 kW) appliance running for 1 hour uses 1 kWh of energy. Power × Time = Energy.
These conversions use internationally recognized standard conversion factors: 1 hp (mechanical) = 745.7 W, 1 PS (metric) = 735.5 W, 1 BTU/h = 0.293071 W. Results are calculated with full precision and displayed to appropriate significant figures for practical use.
Different horsepower standards evolved in different regions. Mechanical horsepower (745.7 W) is used in North America and Britain. Metric horsepower or PS (735.5 W) is used in continental Europe and Asia. Electrical horsepower (746 W) is sometimes used for electric motors. The differences reflect historical measurement practices.
List all running appliances and their power ratings (in watts). Add them together for total power demand. For example: lights (200 W) + refrigerator (150 W) + TV (100 W) + AC (3,500 W) = 3,950 W or about 4 kW. This helps size generators or solar systems.
Yes, all power units can be converted to each other because they all measure the same thing - the rate of energy transfer. This converter uses watts as the common reference, converting your input to watts first, then to all other units. This ensures consistency and accuracy across all conversions.