Units & measurement
Power Conversion Calculator
Convert a known power value between watts (W), kilowatts (kW), mechanical horsepower (hp) and Btu IT per hour. Calculating electrical power from volts and amps is a different task that may also need power factor and phase details.
67 / CONVERT POWER
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Power quantity
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The same power in electrical, mechanical and thermal units.
Watts (W)
Mechanical horsepower (hp)
Btu IT per hour
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Power conversion formulas and factors
Convert a known power to watts, then divide by the factor for the unit you want. These units describe the same rate of energy transfer.
| Starting power | Equivalent watts | Conversion |
|---|---|---|
| 1 watt (W) | 1 W | W ÷ 1,000 = kW |
| 1 kilowatt (kW) | 1,000 W | kW × 1,000 = W |
| 1 mechanical horsepower (hp) | 745.699871582 W | hp × 745.699871582 ≈ W |
| 1 Btu IT per hour (BTU/h) | 0.293071070172 W | BTU/h × 0.293071070172 ≈ W |
The horsepower and BTU/h factors above are rounded for reading. The calculator uses the declared mechanical horsepower and International Table Btu definitions. Metric, electrical and boiler horsepower are different conventions.
Can I calculate watts from volts and amps?
This tool starts with a known power. Calculating electrical power from voltage and current requires the appropriate DC or AC relationship, including phase and power factor where applicable. Converting electrical input to horsepower also does not establish a motor’s shaft output: efficiency matters. Use the motor efficiency savings calculator to compare entered efficiencies at the same mechanical output.
What is the difference between kW and kWh?
Kilowatts measure power; kilowatt-hours measure energy accumulated over time. A constant 2 kW input for 3 hours uses 6 kWh. Use the energy unit converter for kWh, joules and Btu, or the equipment electricity cost calculator to include running time and an electricity rate.
How the power conversion calculator works
Enter a power value and select its starting unit to see the same quantity in all four units. The calculator first converts the starting value to watts, then divides by each target unit factor. A watt is one joule per second, and 1 kW equals 1,000 W. Power describes the rate of energy transfer; kWh describes energy used or delivered over time.
Mechanical horsepower is defined here as 550 foot-pounds-force per second. The international foot (0.3048 m), international pound (0.45359237 kg) and standard gravity (9.80665 m/s²) give approximately 745.699872 watts per horsepower. Metric, boiler and electrical horsepower use other conventions.
Btu IT per hour uses the International Table Btu of 1,055.05585262 joules divided by 3,600 seconds, giving approximately 0.29307107 W per Btu IT/h. The converted values describe the same power at the same measurement point. Converting an electrical input rating to horsepower does not account for the losses between motor input and shaft output; apply a matching efficiency model when comparing those different measurement points.
Worked example
With 1 entered and kilowatts selected, the results are 1 kW, 1,000 W, approximately 1.341 mechanical hp and 3,412.142 Btu IT per hour. Selecting watts and entering 1,000 returns the same quantities. For the reverse horsepower calculation, 1 mechanical hp is approximately 745.700 W or 0.746 kW. The displayed values are rounded; the CSV retains the underlying numerical results.
Sources and assumptions
The source material explains the underlying calculation or pricing structure. Entered prices, costs, schedules and scenario choices are your assumptions; this tool does not obtain supplier quotes or predict actual results.
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