Power Unit Converter

The Power Unit Converter is a free online tool that convert between watt, kilowatt, megawatt, horsepower (mechanical/metric), btu/hour, calorie/second, and more. It runs entirely in your browser with no installation or sign-up needed.

Mechanical ≈ 745.7W (US/UK), metric ≈ 735.5W (most other countries).

Nine: Watt, kW, MW, HP (mechanical), HP (metric), BTU/hr, cal/s, ft·lbf/s, J/s.

Yes — all client-side.

Absolutely. The Power Unit Converter processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Power Unit Converter is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Power Unit Converter in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Power Unit Converter works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

It depends on which horsepower you mean, because the word covers two different definitions. One mechanical (imperial) horsepower, the figure used in the US and UK, equals about 745.7 watts, so a 1 hp motor draws roughly 0.7457 kilowatts. One metric horsepower — the PS or Pferdestärke quoted across most of Europe and Asia — is slightly smaller at about 735.5 watts. That 1.4% gap means a 100 PS engine abroad is rated near 98.6 hp in the States, which is why the same car can list two different numbers. This converter keeps both types as separate units so you never mix them up, and a live formula line shows the exact factor it applied. Enter your value, pick mechanical or metric horsepower, and read the watt result instantly.

Air conditioners are usually rated in BTU/hour for cooling capacity, but their electrical draw and many engineering specs are in watts, so you often need to bridge the two. The conversion is direct: 1 BTU/hour equals about 0.2931 watts, so a 10,000 BTU/h unit corresponds to roughly 2,931 watts of thermal power. To go the other way, multiply watts by about 3.412 to get BTU/hour. Note that cooling capacity in BTU/h is not the same as the electrical wattage the unit consumes from the wall — that depends on its efficiency rating. This converter has a one-tap preset for a 10,000 BTU/h AC and uses the exact factor 0.29307107, so you can compare a cooling spec against a watt figure without doing the arithmetic by hand. Just enter the BTU/h value and select watts as your target.

Both measure power — the rate energy flows per unit of time — but they come from different systems, so the numbers don't match one-to-one. A watt is the SI unit, defined as one joule per second. A calorie per second is a thermal unit, and one calorie per second equals exactly 4.1868 watts, because one (thermochemical-table) calorie is 4.1868 joules. So a 500 cal/s burner is putting out roughly 2,093 watts of heat. The calorie here is the small gram-calorie, not the food Calorie (kilocalorie) on nutrition labels, which is 1,000 times larger. Mixing those up is a common error when reading older thermal specs. This tool anchors every unit internally to the watt using the exact 4.1868 factor, so calorie-per-second figures convert cleanly to watts, kilowatts, or BTU/hour. Enter the value, choose your target unit, and read the result.

The discrepancy comes from two competing definitions of horsepower rather than any change to the engine. Mechanical horsepower, standard in the US and UK, is fixed at about 745.7 watts. Metric horsepower (PS or CV) used across Europe and much of Asia is defined slightly lower, around 735.5 watts. Because metric horsepower represents less power per unit, the same engine output produces a larger PS number than its hp figure — about 1.4% higher. A motor making 73.5 kilowatts reads as 100 PS but only about 98.6 mechanical hp. Marketing materials, spec sheets, and import paperwork frequently quote whichever standard is local, which is why a single car can appear with two ratings. This converter lists mechanical and metric horsepower as separate units so you can translate between them precisely. Pick both ends explicitly and the formula line confirms exactly which definition is in play.

The conversion is exact to the constants involved, so accuracy is limited only by the decimal precision you choose rather than by rounding shortcuts. Internally every unit is anchored to the watt, so kilowatts convert to horsepower in a single step with no drift between intermediate units. For reference, 1 kilowatt equals about 1.34102 mechanical horsepower or about 1.35962 metric horsepower, and the tool shows the precise factor it used on a live formula line such as "1 kW = 1.34102209 hp(I)." You can set precision to 2, 4, 6, 8, 10, or 12 decimal places depending on whether you need a quick estimate or laboratory-grade figures. The only judgment call is choosing mechanical versus metric horsepower, since those differ by definition. Enter your kilowatt value, select the horsepower type you want, and copy or export the result with confidence.