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Queueing Theory Calculator

Average arrivals per unit time.
Average services per unit time. For a stable M/M/1 queue, μ must be greater than λ.

Result

Calculated result Ready Change any value to calculate instantly.
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M/M/1 queue calculator for arrival rate λ and service rate μ. Requires μ > λ and returns the expected queue length Lq.

Formula

L = λ/(μ-λ); Lq = λ²/[μ(μ-λ)]
  • Queueing Theory Calculator models a stable M/M/1 queue from the arrival rate λ and service rate μ. The model requires μ > λ. It returns Lq, the expected number of customers waiting in the queue, using Lq = λ²/[μ(μ-λ)]; the expected number in the system is L = λ/(μ-λ).
  • The main inputs are Arrival rate λ, Service rate μ. Enter them in the units and format shown in the calculator.
  • Keep comparable quantities in compatible units whenever the formula combines or compares them.
  • Changing any input above recalculates the result with the same calculation engine used by this page.

Example: Queueing Theory

Inputs
  • Arrival rate λ: 2
  • Service rate μ: 3

If λ = 2 arrivals per time unit and μ = 3 services per time unit, L = 2/(3-2) = 2 and Lq = 2²/[3(3-2)] = 4/3 ≈ 1.3333.

Sample result: Calculating…

Frequently asked questions

What condition is required for an M/M/1 queue?

The service rate μ must be greater than the arrival rate λ; otherwise the queue is not stable.

What does Lq mean?

Lq is the expected number of customers waiting in the queue, excluding any customer currently in service.

What does L mean?

L is the expected number of customers in the system, including both the queue and the customer in service.

What does the Queueing Theory calculate?

M/M/1 queue calculator for arrival rate λ and service rate μ. Requires μ > λ and returns the expected queue length Lq.

Which values should I enter?

Enter Arrival rate λ, Service rate μ using the units and format shown beside each field.

What formula does this calculator use?

The calculator uses the following relationship: L = λ/(μ-λ); Lq = λ²/[μ(μ-λ)].

Page information

Updated: October 8, 2026