Free Excel template · Call Center

Call Center Staffing (Erlang) Worksheet

A consultant-grade staffing model that turns call volume, handle time, target service level and shrinkage into the number of agents you need. It computes offered load in Erlangs, base and shrinkage-adjusted agent requirements, a full hour-by-hour day plan, a fully-loaded labor cost, and an AHT sensitivity view that shows how handle time drives headcount and budget.

✓ Instructions
✓ Staffing Calculator
✓ Day Plan
✓ Cost

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Excel template · FreeCall Center Staffing (Erlang) Worksheet

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Free Excel template

Spotsaas · 2026

Call Center Staffing (Erlang) Worksheet

✓ Instructions

✓ Staffing Calculator

✓ Day Plan

✓ Cost

Get the worksheet →

What it is

The Call Center Staffing (Erlang) Worksheet is a consultant-grade spreadsheet that answers the single most expensive question in contact-center operations: how many agents do I actually need? You enter your forecast call volume, your average handle time (AHT), the service level you’re targeting — the classic 80/20, meaning 80% of calls answered within 20 seconds — and your shrinkage percentage, and the model computes the offered load in Erlangs, the base number of agents required to hit that service level, and the shrinkage-adjusted headcount you must actually roster to cover breaks, training, absence, and shrink.

Staffing math is unintuitive, which is exactly why a worksheet beats a guess. Because of the queuing dynamics behind the Erlang C formula, agent requirements do not scale linearly with volume — doubling calls does not mean doubling agents, and a small change in AHT can swing headcount and budget more than you’d expect. The worksheet captures this directly with an AHT Sensitivity view that shows how a few seconds of extra handle time per call ripples into additional agents and additional cost, and a Day Plan that breaks the requirement down interval by interval so you staff to the morning peak rather than the daily average.

Beyond raw headcount, the workbook closes the loop on cost. A Cost sheet turns the agent requirement into a fully-loaded labor figure, and a Summary sheet pulls the key outputs — required agents, service level, occupancy, and cost — into one place you can drop into a plan or a budget request. It is the bridge between a demand forecast and a defensible staffing and budget decision.

What it's used for

Staffing is where forecasting meets money: roster too few agents and service level collapses with abandoned calls and angry customers; roster too many and you burn budget on idle occupancy. This worksheet exists to find the defensible middle. Teams use it to:

✓ Convert a call-volume forecast and AHT into a hard agent requirement using Erlang C, instead of estimating headcount from a ratio or last year’s roster.
✓ Translate a service-level target like 80/20 into the precise number of agents needed to hit it, and see how relaxing or tightening the target changes headcount.
✓ Apply a realistic shrinkage percentage so the rostered headcount accounts for breaks, training, meetings, and absence — not just bodies on the phone.
✓ Build an interval-by-interval Day Plan that staffs to peaks and troughs rather than to a flat daily average that leaves the morning rush under-covered.
✓ Run AHT sensitivity analysis to quantify how a process change, a new script, or a system slowdown that adds seconds to handle time drives both headcount and budget.
✓ Produce a fully-loaded labor cost for a queue or campaign that finance can review and approve as part of a budget request.
✓ Stress-test occupancy so the plan doesn’t quietly run agents at an unsustainable utilization that drives burnout and attrition.

Who uses it

Staffing decisions sit at the intersection of operations, finance, and the front line, so the worksheet draws in several roles — each looking at a different output of the same model:

Workforce Management (WFM) AnalystsThis is their core tool — they feed in the forecast and AHT, tune service level and shrinkage, and produce the interval requirements that become the schedule.

Contact Center Operations ManagersThey use the headcount and service-level outputs to decide whether the current team can hit targets, and to justify hiring or overtime when it can’t.

Finance / FP&A PartnersThey lean on the Cost and Summary sheets to turn an agent requirement into a fully-loaded labor budget and to challenge the assumptions behind it.

Team Leads / SupervisorsThey consume the Day Plan to understand why coverage is tight at certain intervals and to manage breaks and offline activities around the peaks.

Call Center ConsultantsThey use the model to size a new operation or a new campaign for a client, presenting the Erlang math as the defensible basis for a staffing recommendation.

Startup founders launching a support lineBefore licensing a platform like Five9 or CloudTalk, they use the worksheet to sanity-check how many agents — and how much budget — a given volume and service-level promise will actually require.

Context & good to know

Erlang C — the queuing formula at the heart of this worksheet — has been the standard for inbound call center staffing for decades, and for good reason: it captures the non-linear relationship between offered load, agent count, and the probability a caller waits. The counterintuitive lesson it teaches every WFM analyst is that the last increment of service level is the most expensive. Going from 80/20 to 90/10 can cost a surprising number of extra agents because you are now staffing for ever-rarer simultaneous spikes. The worksheet makes that trade-off visible so leaders choose a service-level target with eyes open.

Most contact-center platforms — Talkdesk, Five9, Genesys Cloud, Nextiva, CloudTalk — include dashboards that report service level, occupancy, and AHT in real time, and dedicated WFM suites like Calabrio One automate forecasting and scheduling end to end. But the planning math still has to happen somewhere, and a transparent spreadsheet is where many teams do it because every assumption is visible and adjustable. The agent requirement this worksheet produces is also the input the WFM Shift Schedule template needs to check coverage — the two are designed to work together, with staffing math feeding scheduling reality.

When buyers ask how much call center software costs, the licensing fee is usually the smaller number. Labor is the dominant cost of running a contact center, often the large majority of the total, which is exactly why getting staffing right matters more than shaving a few dollars off a per-seat price. This worksheet exists to make the labor number defensible and to expose the levers — AHT, shrinkage, service level — that move it most, so an operations leader can have an informed conversation about where to spend and where to trim.

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FAQ

Questions, answered

What is the Erlang C formula and why is it used for staffing?

Erlang C is a queuing model that predicts the probability a caller has to wait, given the offered call load and the number of agents available. It’s the standard for inbound call center staffing because it accounts for the random, bursty nature of call arrivals — something a simple ratio can’t do. From it you derive how many agents are needed to hit a given service level, and how occupancy and wait times change as you add or remove staff.

What is an Erlang and what does “offered load” mean?

An Erlang is a unit of telephone traffic representing one hour of continuous call activity. Offered load — measured in Erlangs — is your call volume multiplied by AHT over a period, expressed as the equivalent number of agent-hours of work arriving. It’s the raw demand figure the Erlang C model needs before it can tell you how many agents are required to serve that demand at your target service level.

What is service level 80/20?

Service level 80/20 means 80% of calls are answered within 20 seconds. It’s the most widely cited contact-center service-level target, though it’s a convention, not a law — some operations target 90/15 or 70/30 depending on cost and customer expectations. The worksheet lets you set whatever target you want and shows how many agents it takes to hit it, so you can weigh the cost of a tighter target against the experience benefit.

What is shrinkage and why must I include it?

Shrinkage is the percentage of paid time agents are not available to take calls — breaks, training, meetings, coaching, system issues, and unplanned absence. It commonly runs 25-35%. If you staff only to the Erlang base requirement and ignore shrinkage, you will be chronically understaffed, because a meaningful share of your rostered agents won’t actually be on the phone at any given moment. The worksheet inflates the base requirement by your shrinkage rate to give a realistic roster number.

Why don’t agents scale linearly with call volume?

Because of pooling and queuing dynamics, a larger operation is more efficient per agent than a small one — a 100-agent queue absorbs random spikes better than ten separate 10-agent queues. So doubling your call volume usually requires less than double the agents to maintain the same service level. This is why the Erlang model matters: a linear estimate will over-staff large queues and badly under-staff small ones.

How does AHT affect headcount and cost?

AHT — average handle time, the talk time plus hold plus after-call work per contact — drives demand directly. Because it multiplies into offered load, even a few extra seconds per call across thousands of calls can require additional agents and add real cost. The worksheet’s AHT Sensitivity view exists to quantify this, showing how handle-time changes from a new script, a slow system, or a process tweak ripple into staffing and budget.

What is occupancy and what’s a healthy level?

Occupancy is the percentage of logged-in time agents spend actually handling contacts versus waiting for the next one. Run it too high — above roughly 85-90% sustained — and agents have no recovery time between calls, which drives errors, lower quality, and burnout-related attrition. The worksheet surfaces occupancy so you can confirm your plan isn’t hitting service level by quietly grinding the team.

How do I build an interval-by-interval Day Plan?

Rather than staffing to a single daily average, you forecast volume for each interval — commonly every half hour — and run the Erlang calculation per interval. The Day Plan sheet does this, producing a required-agent count for each part of the day so you can schedule to the morning peak, the lunchtime dip, and the late surge separately. Staffing to the average alone leaves peaks dangerously under-covered.

How much of a call center’s cost is labor?

Labor is typically the dominant cost of running a contact center — usually the large majority of total operating expense, far exceeding software licensing. That’s why staffing accuracy matters so much: a small percentage improvement in how well you match agents to demand outweighs almost any saving on per-seat software pricing. The Cost sheet turns the agent requirement into a fully-loaded labor figure for exactly this reason.

Can this replace a dedicated WFM tool?

For planning a single queue, a campaign, or a small operation, the worksheet is often enough — it does the core Erlang math transparently. As you scale to many queues, multi-skilled agents, and real-time intraday management, a dedicated WFM suite such as Calabrio One becomes worthwhile because it automates forecasting, scheduling, and adherence at scale. The worksheet is a great way to understand and validate the math those tools run under the hood.

Does the staffing number feed into scheduling?

Yes — the agent requirement this worksheet produces is the input a shift schedule needs. The companion WFM Shift Schedule template takes your interval requirements and checks them against the roster you actually build, showing where you’re over- or under-staffed by daypart. Staffing answers “how many agents,” and scheduling answers “who works when” — you need both, and they share the same numbers.

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