One joule is defined as the amount of work done by a force of one newton moving an object through a distance of one metre. Other relationships are:

While it is dimensionally correct to express joules as newton metres or N·m, such use is discouraged by the SI authority to avoid confusion with torque. Torque and energy are fundamentally different physical quantities. For example, adding 1 N·m of torque to 1 N·m of energy gives a dimensionally consistent result of 2 N·m, but this quantity is physically meaningless.

One joule in everyday life is approximately:

The nanojoule (nJ) is equal to one billionth of one joule. One nanojoule is about 1/160 of the kinetic energy of a flying mosquito.

The microjoule (μJ) is equal to one millionth of one joule. The Large Hadron Collider (LHC) is expected to produce collisions on the order of 1 microjoule (7 TeV) per particle.

The millijoule (mJ) is equal to one thousandth of one joule.

The kilojoule (kJ) is equal to one thousand joules. Food labels in some countries express food energy in kilojoules. One kilojoule is about the maximum amount of solar radiation received by one square metre of the Earth in one second.

The megajoule (MJ) is equal to one million joules, or approximately the kinetic energy of a one-ton vehicle moving at 160 km/h (100 mph).

The gigajoule (GJ) is equal to one billion joules. Six gigajoules is about the amount of chemical energy in a barrel of oil.

The terajoule (TJ) is equal to one trillion joules. About 60 terajoules were released by the nuclear bomb that exploded over Hiroshima.