[1][2] It is defined to be equal to the electric charge delivered by a 1 ampere current in 1 second.

Like other SI units, the coulomb can be modified by adding a prefix that multiplies it by a power of 10.

As with every SI unit named for a person, its symbol starts with an upper case letter (C), but when written in full, it follows the rules for capitalisation of a common noun; i.e., coulomb becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.

[9] By 1878, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb.

The "international coulomb" based on laboratory specifications for its measurement was introduced by the IEC in 1908.