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Power converter

Convert between watts, kilowatts, megawatts, horsepower, BTU/h, tons of refrigeration, dBm, and dBW with one input.

Power conversion

Enter a value, pick the input unit, and choose the output unit to convert power.

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The numeric power value you want to convert.

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Result

Example using default values

Converted power value.

Converted value
0.1 kW

The input value converted to the selected output unit (with unit).

Estimate, not a legal decision

Read methodology

Use the result as decision support and planning help. For high-stakes choices, confirm the details with the relevant authority, lender, employer, or adviser.

Analysis & guidance

  • Thermal and HVAC ready

    BTU rates, therms, tons of refrigeration, and calorie-based units make it easy to compare heating and cooling capacity.

  • Electrical and mechanical coverage

    Convert VA/VAR/kVA/MVA, dBm/dBW, and horsepower variants to watts to line up motor, grid, and RF specs.

  • From CGS to cosmic scales

    Supports erg/s and dyne-based units along with Planck power and solar luminosity for scientific use.

About this calculator

Power units at a glance

Power is the main attribute that shows how fast energy is converted or transferred. Different fields use different units for the same measure—electrical engineers talk in watts and volt-amperes, HVAC technicians use BTU rates and tons of refrigeration, while mechanics most of the time refer to horsepower. Here is a short guide to the units that the converter considers and their equivalents in watts.

SI backbone

  • Watt (W), kilowatt (kW), megawatt (MW), gigawatt (GW), terawatt (TW), petawatt (PW) - The SI unit of power; 1 kW = 1,000 W, 1 MW = 1,000,000 W, and so forth. These are the units to be used for general electrical and mechanical power ratings.

Horsepower family

  • Horsepower (hp) - Mechanical/imperial hp ≈ 745.7 W, usually referred to engines and motors.
  • Metric horsepower (PS) - ≈ 735.5 W, mainly in Europe/automotive specifications.
  • Electrical hp (hp(E)) - ≈ 746 W, a formal electrical definition.
  • Boiler hp (hp(S)/bhp) - ≈ 9,809.5 W, a unit for steam boilers.
  • Hydraulic hp - ≈ mechanical hp, used in fluid power.
  • Refrigeration hp - ≈ 3,517 W (about one ton of refrigeration per hp).

Thermal and HVAC

  • BTU per hour (BTU/h), BTU/min, BTU/s - British Thermal Units per time; 1 BTU/h ≈ 0.293 W.
  • Therm per hour/min/s - 1 therm = 100,000 BTU; mostly seen in gas billing.
  • Calories (cal) and kilocalories (kcal) per second/minute/hour - 1 cal ≈ 4.184 J; heat/food consumption, an old background.
  • Megacalorie (Mcal) / gigacalorie (Gcal) - Bigger thermal energy units per time, sometimes in industrial heat balance.
  • Ton of refrigeration (TR) - 1 TR ≈ 3,516.85 W; the cooling capacity unit.

Mechanical work rates

  • Foot-pound per second/minute/hour (ft·lb/s etc.) - Imperial work rate; 1 ft·lb/s ≈ 1.3558 W.
  • Kilogram-meter per second/minute (kg·m/s etc.) - Metric work rate; 1 kg·m/s ≈ 9.80665 W.

Electrical and reactive power

  • Volt-ampere (VA), kVA, MVA - The total power in AC systems.
  • Volt-ampere reactive (var), kvar, Mvar - The reactive power; it is related to reactive current/voltage.
  • dBm, dBW - Logarithmic power levels with reference to 1 mW (dBm) or 1 W (dBW), mostly in RF/telecom.
  • Coulomb-volt per second, ampere-ohm per second - Simplify to watts; mostly theoretical ones of P = V·I or P = I²·R.

CGS and scientific units

  • Erg per second/minute/hour (erg/s etc.) - 1 erg = 1e-7 J; was used in scientific literature of the past.
  • Dyne·cm/s, dyne·m/s - CGS power forms; 1 dyne·cm/s = 1e-7 W.

Astronomical and extremes

  • Solar luminosity (L☉) - ≈ 3.828e26 W, the Sun's output; good for scaling in astrophysics.
  • Bolometric luminosity - The total radiant power over all wavelengths; most of the time it is given in L☉.
  • Neutrino luminosity - Occasionally quoted for astrophysical events; can also be standardized to watts.
  • Planck power - ≈ 3.63e52 W, a hypothetical upper scale deriving from fundamental constants.

Practical insights for converting power

  • Match unit to context: VA/var/kVA/MVA should be used for sizing of an AC circuit; hp or kW only for motors; BTU/h, TR, kcal/h, or therms for heating/cooling loads.
  • Mind apparent vs real power: kW is the real power, kVA is the apparent power, and kvar is the reactive power of an AC system. Power factor (kW/kVA) is important for both the equipment sizing and that of the grid-penalty avoiding.
  • HP variants differ: Imperial hp (~745.7 W) vs metric hp (~735.5 W) can change the specs by approximately 1-2%. Boiler hp is quite a lot bigger, do not confuse it with mechanical hp.
  • Thermal ratings are not electrically convertible: 1-ton air conditioner (~3.5 kW cooling) does not imply that the device is consuming 3.5 kW of electricity; the real input is determined by the efficiency (EER/COP).
  • RF power in dBm/dBW: The conversions are logarithmic; +10 dB = 10x power, +3 dB ≈ 2x. 30 dBm = 1 W; 0 dBW = 1 W.
  • Great scales: Solar luminosity is mainly used for astrophysical comparisons; Planck power is theoretical—only use it for scaling purposes in thought experiments.
  • Check the time bases: BTU/h vs BTU/min vs BTU/s differ by 60 or 3,600 times; the same goes for cal/min and cal/h. Be sure to compare the same time basis.
  • Cooling vs heating: TR, BTU/h, and kcal/h are typical HVAC units; therms and kW are usually seen in gas and electric heating bills, respectively. Before comparing costs or efficiencies, make sure you convert values to the same baseline (usually kW).

Frequently asked questions

What’s the difference between W and kW?

A kilowatt (kW) is 1,000 watts (W). Use kW for larger values (like appliances or EV charging) and W for smaller loads.

How do I convert horsepower to watts?

Horsepower is a power unit used for engines. The converter lets you choose hp or metric hp (PS) and converts directly to W/kW.

What is dBm?

dBm is a logarithmic power unit referenced to 1 milliwatt. It’s common in RF and networking. Converting to watts depends on the dBm value.

Is BTU/h a power unit?

Yes. BTU per hour (BTU/h) is a rate of energy transfer, commonly used for heating and cooling capacity.

How to read this calculator

These results are meant as guidance. They are based on rules, assumptions, and simplified models that can differ from your exact real-world situation.

Estimate, not a legal decision

Use the result as decision support and planning help. For high-stakes choices, confirm the details with the relevant authority, lender, employer, or adviser.

Methodology

Each calculator uses defined inputs, assumptions, and logic. We explain the broader approach on the methodology page.

Read methodology

Sources and updates

Important calculators should be traceable back to official rules, public guidance, or other clearly stated references.

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