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How do I convert power between watts, kilowatts and horsepower?

Type a value into AnyTool Power Converter and pick the units. It instantly converts both ways between watt, kilowatt, megawatt, gigawatt, milliwatt, all three horsepowers (mechanical 745.7 W, metric/PS 735.5 W, electrical 746 W), BTU/h, kcal/h, foot-pound per second, erg/s and volt-ampere, and shows the value in every unit at once in a copyable table. Everything is calculated in your browser, so nothing is uploaded.

  • Live two-way conversion — type in either field and the other updates
  • All three horsepowers clearly labelled: mechanical/imperial, metric/PS and electrical
  • SI (W, kW, MW, GW, mW) plus BTU/h, kcal/h, ft·lbf/s, erg/s and VA
  • See the value in every unit at once, each row copyable
  • 100% in your browser — no upload, no signup, works offline

What is

Power Conversion

Power is the rate of doing work or transferring energy — one watt equals one joule per second. Power conversion changes that figure from one unit to another, for example kilowatts to horsepower. Every power unit relates to the SI base (the watt) by a single linear factor, so conversion is one multiply and one divide; the key subtlety is that horsepower has three different definitions (mechanical 745.7 W, metric/PS 735.5 W and electrical 746 W).

Converters

Related terms

kW to hpwatts to horsepowerBTU/hmetric horsepower (PS)

Frequently Asked Questions

It depends on the type: mechanical hp is 745.7 W, metric (PS) is 735.5 W and electrical hp is exactly 746 W.

Horsepower has three definitions. One mechanical (imperial) horsepower equals 745.69987 watts (550 ft·lbf/s) and is the US engine unit. One metric horsepower — the European PS, CV or cheval — equals 735.49875 watts (75 kgf·m/s), about 1.4% smaller. One electrical horsepower is defined as exactly 746 watts for electric-motor ratings. For everyday estimates 1 hp ≈ 0.746 kW.

Divide kilowatts by 0.7457 for mechanical hp, or by 0.7355 for metric PS. So 100 kW ≈ 134 hp.

To convert kilowatts to mechanical horsepower, multiply by 1000 and divide by 745.69987 — equivalently multiply kW by about 1.34102. For metric horsepower (PS) divide by 735.49875 instead, so multiply kW by about 1.35962. For example, 100 kW is roughly 134.1 hp(I) or 135.96 PS, which is why car specs often quote a slightly higher PS number than hp.

One BTU per hour is 0.29307107 watts, so 1 kW ≈ 3412 BTU/h.

One British thermal unit (IT) per hour equals 0.29307107 watts. To convert BTU/h to watts multiply by 0.293071; to go the other way divide. This is the standard HVAC unit: a 12,000 BTU/h air conditioner is about 3.5 kW, which is also called one ton of cooling.

No. Every calculation runs in your browser, so nothing is sent to a server and it works offline.

AnyTool Power Converter computes every result locally in JavaScript using exact factors through a watt base. No value is uploaded, there is no tracking, and the page keeps working offline after the first load.

Detailed Explanation

Methodology

How the Power Converter Works

AnyTool Power Converter performs every calculation in the browser. Each unit declares a single linear factor relative to a shared watt base — the exact number of watts in one of that unit — so any unit converts to any other through watts without an N-by-N table. The factors are the internationally-agreed definitions: a kilowatt is 1000 W, a megawatt 1e6 W, a gigawatt 1e9 W and a milliwatt 0.001 W. Crucially, horsepower has three distinct definitions and the tool labels all three: mechanical/imperial horsepower is 745.69987 W (550 ft·lbf/s), metric horsepower (PS / CV / cheval) is 735.49875 W (75 kgf·m/s), and electrical horsepower is exactly 746 W. It also covers thermal and other units: a BTU/h is 0.29307107 W, a kilocalorie/hour 1.163 W, a foot-pound per second 1.3558179 W, an erg/s 1e-7 W, and a volt-ampere 1 W at unity power factor. A value is multiplied to watts and then divided into the target unit.

  • Thirteen units spanning SI, mechanical, thermal, CGS and electrical systems
  • The watt is the shared base; each unit is one exact factor
  • Three horsepowers labelled: mechanical 745.7 W, metric/PS 735.5 W, electrical 746 W
  • Conversion is value to base to value, so any unit maps to any other
  • All arithmetic is client-side JavaScript — no server round-trip
How It Works

All Units, Precision and Reference

A single input is converted into every power unit at once in a copyable table, with the source and target rows highlighted. A decimals control sets precision from 0 to 10 places, and magnitudes that are very large or very small automatically switch to scientific notation so results stay readable. A formula reference, a common-conversions list and a units-at-a-glance table (showing each unit in watts and which measurement system it belongs to) accompany the converter, plus a note explaining how the three horsepower definitions differ.

  • Convert-to-all table shows the value in every unit simultaneously
  • Each unit row is individually copyable
  • Adjustable precision from 0 to 10 decimal places
  • Automatic scientific notation for extreme magnitudes
  • Built-in horsepower-variant note and a units-by-system table
Privacy & Security

Privacy and Offline Use

Because all conversion runs in the browser, no value is sent to a server, there is no account or tracking, and the page works offline after first load. The converter is built on a shared, unit-tested conversion engine that other AnyTool unit converters reuse, so behaviour is consistent across the site.

Power conversion: in-browser (AnyTool) vs typical online converters
CapabilityAnyToolTypical online converters
ProcessingRuns in your browserOften server-side
Units13: SI, mechanical, thermal, CGS and electricalOften W, kW and one hp only
HorsepowerAll 3 labelled (mechanical, metric/PS, electrical)Frequently a single ambiguous "hp"
Factor accuracyExact definitions (metric hp = 735.49875 W)Frequently rounded constants
Two-way inputEdit either field, both updateUsually one-direction with a button
All units at onceYes, copyable tableOften one target at a time
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool converts every power unit locally through an exact watt base and uploads nothing.