The **joule-second** (**J s** or **J·s**) is a unit equal to a joule multiplied by a second, used to measure action. The action of a system has the dimensions of energy integrated over time; it is therefore measured in joule-seconds. The joule-second is the unit used for Planck's constant. It is also the unit for the angular momentum of a rotating object.

In SI base units, the joule-second is