The joule (symbol J, also called newton meter, watt second, or coulomb volt) is the SI unit of energy and work. The unit is pronounced to rhyme with "tool", and is named in honor of the physicist James Prescott Joule (1818-1889).

1 joule = 1 N · 1 m = 1 newton · 1 metre = 1 kg · 1 m² · 1 s⁻²

1 joule = 1 C · 1 V = 1 coulomb · 1 volt

1 joule = 1 W · 1 s = 1 watt · 1 second

One joule is the work required to exert a force of one newton for a distance of one metre, so the same quantity may be referred to as a newton metre or newton-metre (also with meter spelling), symbol N·m or N m. However, to avoid confusion the newton metre is usually used as a measure of torque, not energy.

Another way of visualizing the joule is the work required to lift a mass of about 102 g (e.g. a small apple) for one metre under the earth's gravity.

One joule is also the work required to move an electric charge of 1 coulomb through an electrical potential difference of 1 volt.

One joule is also the work done to produce power of one watt for one second, such as when somebody takes one second to lift the small apple mentioned above through one metre under the earth's gravity.

1 joule is equal to:

• c. 2.78 × 10⁻⁷ kW·h (kilowatt hour)
• c. 0.239 cal (calorie)
• c. 0.000 948 BTU (British thermal unit)
• c. 0.738 ft·lbf (foot pound force)
• 1 W·s (watt second)
• 1 N·m (newton metre)
• c. 23.7 ft·pdl (foot poundals)
• 10 000 000 erg (ergs)

See also

• conversion of units
• SI prefixes
• Orders of magnitude
• eV
• kWh
• TWh
• 1 E0 J for further comparisons