Erlang C Isn’t Broken — But Your Workforce Planning Might Be
Erlang C remains one of the most recognised and widely used workforce planning models in contact centres, and for good reason. It is simple, fast and still useful for estimating staffing requirements in traditional voice environments.
But while Erlang C is not broken, many contact centres are now applying it to environments it was never designed for. Voice is no longer the only workload. Channels behave differently. Concurrency matters. Skill-based routing matters. Real-time volatility matters.
That does not mean Erlang should be thrown out. It means leaders need to understand where it helps, where it falls short, and what more mature workforce planning approaches look like in modern contact centres.
In this article, I explain what Erlang C still does well, where it starts to break down, what leading contact centres are using instead, and the practical next steps I believe contact centres should consider if they want to strengthen workforce planning capability.
The Real Issue Isn’t Erlang. It’s Over-Reliance.
There is a lot of industry noise at the moment suggesting that “nobody uses Erlang anymore” or that it has become obsolete. That is too simplistic.
The reality is that many contact centres still use Erlang C, either directly in spreadsheets and calculators, or indirectly through workforce management tools that still incorporate queueing logic as part of a broader planning engine.
The problem is not that Erlang exists. The problem is when it becomes the only lens through which staffing decisions are made in environments that are now multi-channel, skill-based, highly variable and increasingly dynamic.
What Erlang C Still Does Well
It is important not to dismiss Erlang C just because the operating environment has changed. The model still provides genuine value when used appropriately.
At its core, Erlang C helps contact centres understand the relationship between call volume, average handle time, service level targets and the number of people required to answer demand. That remains useful, especially for voice-led environments where assumptions are relatively stable.
📊 Fast baseline modelling
Erlang gives planners and leaders a quick way to estimate staffing needs without the complexity of a full simulation model.
🎓 Great for education
It helps explain why service level, occupancy, delays and resourcing are tightly connected rather than independent decisions.
☎️ Useful in simpler environments
Where voice is the dominant channel, routing is straightforward and variability is moderate, it can still be directionally sound.
🧭 Strong as a reference point
Even advanced workforce management environments often use Erlang-style logic as a baseline before layering in more complex assumptions.
That is why ACXPA continues to provide a free online Erlang C Calculator and a practical glossary explanation of Erlang C.
These are still valuable resources. The mistake is not using them. The mistake is believing they tell you everything you need to know.
Where Erlang Starts to Break Down
Erlang C was built for a much narrower operating context than most contact centres now deal with. Once an organisation moves beyond a relatively simple voice queue, the model starts to lose explanatory power.
📱 Multi-channel operations
Modern contact centres are not just managing phone calls. They are dealing with chat, messaging, email, social channels and increasingly asynchronous workloads. Each channel behaves differently. Customer expectations differ. Response logic differs. Work pacing differs.
🔄 Concurrency
One of the biggest shifts in recent years has been the growth of channels where agents can handle more than one contact at a time. Chat is the obvious example, but messaging and asynchronous work create similar issues. Capacity is no longer simply one person handling one interaction.
⏳ Customer patience and abandonment behaviour
Erlang assumes relatively structured waiting behaviour. In reality, customer patience is highly variable. It changes by channel, by intent, by time of day, by urgency and by expectations created elsewhere in the journey.
🧠 Skill-based routing and blended teams
Many contact centres now have agents with overlapping skills, specialist queues, priority handling rules, overflow logic and blended work types. In those environments, staffing is not simply about putting enough people into one queue. It is about modelling capability, routing and utilisation across a more complex system.
⚡ Volatility and real-world messiness
Erlang relies heavily on averages. Average handle time. Average arrival rates. Average conditions. But contact centres do not operate on averages. They operate on spikes, peaks, disruptions, campaigns, outages, roster gaps, process failures and sudden shifts in demand.
Erlang gives you a number. Modern operations need a range, a risk profile and a response plan.
That is the real planning challenge. Not simply calculating what should happen if assumptions hold, but understanding what happens when they do not.
What Leading Contact Centres Are Using Instead
There is no single “new Erlang” that has replaced the old model. The shift is broader than that.
Leading contact centres are moving from formula-led planning to system-led planning. That means using tools, methods and operational disciplines that reflect how the contact centre actually behaves rather than trying to force everything into a single queueing formula.
🧪 Simulation-based planning
Discrete event simulation and other scenario-based approaches model the broader system, including arrivals, routing, channel mix, agent skills, customer patience and variability. Instead of giving one fixed answer, simulation helps planners understand a range of possible outcomes under different conditions.
🤖 AI-driven forecasting
Forecasting is moving beyond simple year-on-year trends and static historical averages. More mature environments now incorporate seasonality, external events, campaigns, billing cycles, outages, anomaly detection and more frequent reforecasting logic.
💬 Multi-channel workload modelling
Rather than forcing all work into a voice planning model, advanced centres model channels differently based on service expectations, pacing, concurrency and work type. This is particularly important where chat and messaging volumes are growing quickly.
📈 Real-time optimisation
Leading operations do not just build a plan and hope it holds. They reforecast intra-day, monitor adherence and queue performance closely, and adjust staffing or routing based on emerging conditions throughout the day.
Why This Matters Operationally
Some leaders hear conversations like this and assume it is just technical WFM debate. It is not. The quality of your planning model has very real consequences across the operation.
😊 Customer experience
Underestimating demand or misunderstanding channel behaviour leads directly to longer waits, missed SLAs, higher abandonment and more effort for customers.
👥 Employee experience
Weak planning creates avoidable pressure on frontline teams, higher occupancy, more volatility and greater burnout risk.
💰 Financial performance
Poor planning can drive both overstaffing and understaffing at different times, which means you can spend too much while still delivering poor outcomes.
🎯 Leadership confidence
When workforce planning outputs repeatedly fail to match lived operational reality, confidence in planning disciplines erodes and decisions become more reactive.
🌐 Digital channel growth
Centres expanding self-service, chat, bots or asynchronous support need planning models that reflect how those channels actually behave rather than pretending they are just voice with different labels.
This is why the most capable contact centres do not ask, “Should we stop using Erlang?” They ask, “What is Erlang still useful for, and what else do we need around it?”
Practical Next Steps for Contact Centres
For most organisations, the answer is not to rip out existing planning logic overnight. The more practical path is to raise planning maturity step by step.
Stress-test your current assumptions
Look at where your planning outputs regularly diverge from operational reality. Are your volumes more volatile than you assume? Are digital channels distorting workload in ways your model does not capture? Is customer patience changing?
Start thinking in scenarios, not just targets
Instead of focusing only on a single staffing number, ask what happens if conditions shift. What if volume spikes? What if AHT climbs? What if a digital campaign lands harder than expected?
Model channels differently
Voice, chat, messaging and asynchronous work should not all be treated as if they behave the same way. The more your operation blends channels, the more important this becomes.
Review whether your tools match your complexity
If your current WFM environment cannot help you model concurrency, scenario risk or real-time optimisation, it may be time to review alternative approaches and technology.
Useful ACXPA Resources
If this article has highlighted gaps in your current approach, ACXPA already has a number of useful resources to help you take the next step.
Summary
Erlang C still has a place in contact centre workforce planning. It is useful, practical and still relevant in the right context. But treating it as a complete answer in a modern contact centre is where the real problem begins.
The most capable operations are not simply replacing Erlang with another formula. They are widening the planning lens. They are using scenario thinking, simulation, improved forecasting, multi-channel modelling and real-time optimisation to better reflect operational reality.
So the question is not whether Erlang is dead. It is whether it is telling you enough.
The centres pulling ahead are not using a magic formula. They are using a better model of reality.
- About the Author
- Latest Articles
After spending over 30 years working in contact centres and CX, one thing I’ve learnt is there is always something more to learn!
I’m thrilled to be the inaugural CEO of ACXPA, and together with the rest of the team, we’re focused on helping Australian businesses deliver efficient and effective customer experiences via phone, digital and in-person by empowering their employees with the skills, industry insights and professional support networks they need to succeed.
