What is the dimension of potential energy?

The dimensional formula for potential energy is [M][L]²[T]⁻².

Basically, it's the same as the dimension for work or any other type of energy. The easiest way to remember this is to use the formula for gravitational potential energy, which is mgh. Here, mass (m) has the dimension [M]. Acceleration due to gravity (g) is [L][T]⁻². And height (h) is a length, so it's [L]. When you multiply them all together, you get [M][L]²[T]⁻². So, it is mass times length squared, divided by time squared. A very fundamental concept, actually.