Why are volts equal to joules per coulomb?

In physics, the volt is the SI unit used to measure electric potential and potential difference. It is defined as joules per coulomb because electric potential represents the amount of work required to move a unit charge against an electric field.12

Since work is measured in joules and electric charge is measured in coulombs, the potential difference between two points is essentially the energy per unit charge. By analogy, if an electric field is defined as force per unit charge, electric potential is defined as potential energy per unit charge. Therefore, one volt is equivalent to one joule of work performed to move one coulomb of charge.12