Westbay Traffic Calculators

A Windows Erlang traffic calculator for sizing trunk groups, and call center queuing calculations. All our licences are for life and include free upgrades.

Westbay Traffic Calculators - Extended Erlang B

Before we launched Westbay Traffic Calculators, industry specialists who needed to use Erlang B to design their trunk groups needed to look traffic figures up in huge books of Erlang B tables. Now, you can perform Erlang calculations instantly on your Windows computer (any version, 32 or 64 bit). This has remained our best-selling product since we launched it in 1996.

“Beats the heck out of lugging around your Erlang tables. I recommend this product highly.”
Computer Telephony Magazine

Download the industry-standard Erlang calculation tools with lifetime upgrades and installation support for a once-only payment of just $99.

Erlang B Calculator

Each traffic calculator is presented inside a tab at the top of the application. Erlang B is an established traffic model for estimating the number of telephone lines you need in a system if you know the busy hour traffic it will have to handle. The Erlang B calculator works up to 90,000 lines.

Westbay Traffic Calculators - Erlang B
“How many lines do I need in my trunk group if it is offered 200 Erlangs of traffic during its busy hour and I accept that 1.2% of my calls will fail due to blocking?”
Answer – 220

You can also perform these calculations in reverse. For example, you can find out what the probability of blocking would be for a given busy hour traffic figure and trunk group size. If you know two of the variables, you can work out the third. The second tab holds an extended version that takes immediate call retries into account.

Call Minutes Calculator

Sometimes it can be more convenient to specify your traffic in terms of minutes of calls per day rather than busy hour traffic in Erlangs. This calculator lets you do that and works up to 30 million minutes of calls per day.

Westbay Traffic Calculators - Call Minutes
“How many lines does my trunk group need? It is offered 50,000 minutes of calls per day and I accept that 3% of calls will be blocked. I estimate that 19% of daily calls are made during the busiest hour?”
Answer – 168

Again, you can perform the calculation in reverse to estimate the number of minutes of calls that your existing trunk group can handle.

Erlang C Calculator

Erlang C models systems that involve queuing, so it’s perfect for working out how many agents you need answering calls at your inbound call center or estimating your existing staff’s expected performance. It works up to one million calls per hour.

Westbay Traffic Calculators - Erlang C
“What percentage of calls will my call center answer within 20 seconds if it receives 650 calls in an hour and it’s manned with 34 available agents?”
Answer – 94%

You can find the answers to such questions as:

  • How many agents does my call center need?
  • How many calls can my operators handle?
  • What duration of calls can we handle?
  • What will the average delay to my incoming calls be?
  • How many calls will we answer within target?


Westbay Traffic Calculators is installed with an illustrated user guide and help system. You’re welcome to contact us if you have any questions about the software, but please check the Westbay Traffic Calculators FAQ first.

Purchase and download

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“I’m really happy with my decision to purchase this software… your company is doing an outstanding job is this area.”
Osvaldo Velarde, Citicorp

Westbay Traffic Calculators can be working on your PC within five minutes for a once-only licence fee that entitles you to free upgrades for life. Please choose the licence type you need:

Single user
Installation on a single PC
Site Licence
Unlimited installations in one building of your company
Global Licence
Installation on any of your company’s PCs worldwide