What is rotational kinetic energy measured in?

Rotational kinetic energy is measured in Joules (J) in the SI unit system.

Here's a breakdown of the units:

The unit of rotational kinetic energy is the same as any form of energy, and the standard unit is the Joule. The reference specifies the units in both the SI and MKS systems:

• SI unit system: Joules (J)
• MKS unit system: kg⋅m²⋅s^-2

These units are equivalent; a Joule is defined as kg⋅m²⋅s^-2.