watt

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watt

unit of measurement

Also known as: W

Written and fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Apr 21, 2025 • Article History

Related Topics:: International System of Units; power; unit

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News •

McKenzie accuses Watt of ‘lying’ over Medicare claims – as it happened • Apr. 20, 2025, 9:28 AM ET (The Guardian)

Immaculate’s Watt smashes Class Four high jump record three times • Mar. 29, 2025, 4:00 AM ET (The Gleaner)

watt, unit of power in the International System of Units (SI) equal to one joule of work performed per second, or to 1/746 horsepower. An equivalent is the power dissipated in an electrical conductor carrying one ampere current between points at one volt potential difference. It is named in honour of James Watt, British engineer and inventor. One thousand watts equal one kilowatt. Most electrical devices are rated in watts.