Kingman's Formula

An approximation for the mean waiting time in queue (commonly used for the single‑server G/G/1 model) that expresses expected queueing delay as a function of server utilization and arrival/service variability; one common form is Wq ≈ (ρ/(1−ρ)) · ((ca^2 + cs^2)/2) · (1/μ), where ρ = λ/μ, ca^2 and cs^2 are squared coefficients of variation of interarrival and service times, and μ is the service rate