Little's law states that, under steady state conditions, the mean number of items in a queuing system equals the mean rate at which the items arrive multiplied by the mean time that an item spends in the system. Algebraically, this can be expressed as
 |
where 
denotes the mean
number of items in the queuing system, 
is the mean number of items
arriving per unit time, and 
is the mean residence time for an item within the system.
Due to its use of general language and its natural conditions with practically no extraneous assumptions, Little's law can be used to asymptotically
describe conditions across a vast array of scenarios. For example, Little's law suggests
that, in steady state, a college 
with 6,000 student admissions per year and a mean
student residence time of two years has a mean enrollment
of 
.
