What does watt mean?
A watt, abbreviated W, is the International System of Units’ unit of power, equal to one joule per second. The term is used especially in electrical and engineering contexts, where the power consumption or output of appliances, light bulbs, batteries, and other devices is stated in watts. For example, a bulb may be labelled “60 watts,” while a home electricity meter may report power usage in kilowatts. A watt measures the rate at which energy is transferred or work is done, not the total amount of energy used; energy over time is measured in watt-hours or kilowatt-hours. In everyday speech, the word is widely understood even when the underlying physics is not. Its name honors James Watt, the eighteenth- and nineteenth-century engineer whose improvements to steam engines made him one of the central figures in the history of power generation.
nounA unit of power in the International System of Units, equal to one joule per second. It is named after the Scottish engineer James Watt.
- The SI unit of power, equal to one joule per second; in everyday use, it appears in appliance ratings and electrical specifications.
"The LED lamp uses only six watts."
"The heater is rated at 1,500 watts."
"A 60-watt light bulb consumes less electricity than a traditional incandescent bulb of the same brightness."
Use the plural when stating a quantity of power or a device's rated output.
"The computer uses 300 watts while it is running."
A watt is a unit of power, but the word also preserves the name of James Watt, whose steam-engine improvements helped transform the Industrial Revolution.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does watt come from?
The word “watt” comes from the surname of Scottish engineer James Watt, who developed important improvements to the steam engine. During the nineteenth century, “watt” was adopted as a unit of power in his honor, following the established practice of naming units after notable scientific figures. Compounds and prefixed forms such as “watt-hour,” “kilowatt,” and “megawatt” developed from this specialized unit name.
Related word forms
How watt is actually used
“Watt” is primarily technical but common in descriptions of electrical appliances and lighting. Use the singular for one unit and “watts” for a quantity or rating. The SI symbol is a capital “W”, and compounds such as “watt-hour” are hyphenated.
Easily confused with watt
“Watt” is a unit of power, while “what” is a word used to ask questions or express surprise.
“Watt” is pronounced like “wait” in many accents, but it names a unit of power, whereas “wait” means to stay or pause.