Electric potential is also known as voltage, which is measured in volts.
Voltage (which measures the work done per charge) is calculated by the formula #V = W / Q#, where #W# represents work, and #Q# is the amount of charge. This means that
#1 V = 1 J/C#
Electric potential difference is usually measured using a voltmeter, which is placed around the object (in parallel) causing the electric potential difference. This could be around a cell, showing the increase in voltage, or around a resistor, showing the drop in voltage.
It is only differences in potential that can be measured. As with all forms of potential energy a reference point or ground needs to be specified in order to make the concept of electric potential meaningful.