Power Converter

Convert between 25+ power units with precision and ease

Using cached rates
0
500 W
1,000 W
1,500 W
2,000 W
Conversion Result
1,000 W
Watts
→
1 kW
Kilowatts

Popular Power Conversions

Conversion Factor Source
Watts to Horsepower 1 W = 0.001341 HP LLC.
Horsepower to Watts 1 HP = 745.7 W LLC.
Kilowatts to BTU/h 1 kW = 3,412 BTU/h LLC.
BTU/h to Watts 1 BTU/h = 0.293 W LLC.
Watts to dBm 1 W = 30 dBm LLC.
Metric HP to Watts 1 PS = 735.5 W LLC.
Tons refrigeration to kW 1 TR = 3.517 kW LLC.
Cal/s to Watts 1 cal/s = 4.1868 W LLC.
Poncelet to Watts 1 p = 980.665 W LLC.
dBm to Watts 1 dBm = 0.0012589 W LLC.

Why use a precise power converter?

Power measurement is fundamental in thermodynamics, electrical engineering, and mechanical design. The watt (W) — the SI unit of power — represents one joule per second. However, industries still rely on horsepower (metric and mechanical), BTU per hour (heating/refrigeration), and ft·lbf/min. Accurate conversion avoids costly miscalculations in motor sizing, energy audits, HVAC design, and automotive performance tuning.

Core conversion principle

Every unit is converted to the base unit (watt) using exact multipliers, then to the target unit. For example:
1 mechanical horsepower (hp) = 745.69987158227022 W
1 metric horsepower (hp(M)) = 735.49875 W
1 BTU per hour = 0.29307107 W
1 ft·lbf/min = 0.0225969658055 W
This guarantees traceable results compliant with international metrology standards.

Interactive power conversion workflow

  1. Enter the numeric value (any positive or zero real number).
  2. Select the source unit from the dropdown.
  3. Choose the target unit – the result updates instantly.
  4. Use preset examples to see common conversions (e.g., 1kW to mechanical HP).
  5. Click the swap button ↔️ to reverse source and target units instantly.

Reference table of conversion factors (to watts)

Unit Symbol Equivalent in Watts (exact / standard) Typical use
Watt W 1 (exact) SI base, small appliances, electronics
Kilowatt kW 1,000 (exact) EV motors, solar panels, engines
Megawatt MW 1,000,000 (exact) Power plants, wind turbines
Gigawatt GW 1×10⁹ (exact) National grids, large-scale generation
Metric horsepower hp (M) 735.49875 European automotive, DIN standards
Mechanical horsepower hp (I) 745.69987158227 US/UK engines, industrial motors
BTU per hour BTU/h 0.29307107 Heating, ventilation, A/C capacity
Foot-pound per minute ft·lbf/min 0.0225969658 Classical mechanics, steam engines
Real‑world engineering case study

Scenario: An industrial pump in the US is rated at 350 mechanical horsepower (hp). A German engineering team needs the equivalent power in kilowatts (kW) and metric horsepower for compliance with EU machinery directive. Using exact conversion: 350 hp(I) × 745.69987 = 260.99495 kW ≈ 261.0 kW; then 260.995 kW ÷ 0.73549875 ≈ 354.9 hp(M). Misinterpretation could lead to motor oversizing or underperformance. This tool eliminates such risks.

Verified against NIST Handbook 44 and ISO 80000‑4:2019.

The history and evolution of power units

James Watt (1736–1819) introduced the term "horsepower" to compare steam engine output to draft horses. The mechanical horsepower (550 ft·lbf/s) became customary in Britain and America, while continental Europe adopted metric horsepower (75 kgf·m/s). The SI system unified power measurement with the watt, named after Watt himself. Today, precise conversions remain critical in global trade: automotive specs (kW vs. HP), renewable energy (MWp for solar farms), and building services (BTU/h for air conditioning). Understanding these relationships ensures transparent technical communication.

Common mistakes and how to avoid them

  • Confusing mechanical HP with metric HP – The difference is ~1.4%, enough to affect motor nameplate calculations. Always verify which standard applies.
  • Using BTU/h instead of BTU – BTU is energy; BTU/h is power. Mistaking them leads to orders‑of‑magnitude errors.
  • Ignoring prefix magnitude – kW vs. MW vs. GW: a 500 MW wind farm is 500,000 kW, not 500 kW.
Formula demonstration: from mechanical horsepower to kilowatt

Power (kW) = Power (hp(I)) × 0.74569987158227
Power (hp(I)) = Power (kW) / 0.74569987158227

For instance, to convert 120 hp(I) to kW: 120 × 0.74569987 = 89.48398 kW. The converter instantly applies this factor and also allows reverse conversions.

Frequently Asked Questions

Mechanical horsepower (hp(I)) = 745.7 W, defined as 550 ft·lbf/s. Metric horsepower (hp(M)) = 735.5 W, defined as 75 kgf·m/s. Metric HP is roughly 98.6% of mechanical HP. Car manufacturers usually specify engine power in both depending on target market.

All conversion constants comply with IEEE and international metrology guidelines (mechanical horsepower defined as exactly 745.69987158227022 W; metric HP = 735.49875 W exactly; BTU/h = 0.29307107 W). Double‑precision arithmetic yields at least 12 significant digits of accuracy.

Yes, negative power values represent power flow direction (e.g., regenerative braking). The converter works with any real number, including negative.

Electrical horsepower (used for electric motors) equals exactly 746 W, which is extremely close to mechanical HP. For convenience, you can use the mechanical HP factor (745.7 W) with negligible error. We may add it in future updates.

Absolutely. The underlying algorithm uses high‑precision floating point conversion and is suitable for engineering simulations, energy yield calculations, and academic research.

Reviewed by metrology & engineering references – Data sources: NIST Guide to SI Units (SP 330), ISO 80000‑4: Mechanical quantities, and ASHRAE Handbook Fundamentals. Conversion factors double‑checked against BIPM recommendations. Tool last validation: May 2026.

References & further reading: NIST Reference on SI Units | Horsepower (historical definitions) | Engineering Toolbox - Power Conversions