Multi-channel staffing calculator

Why not just add the numbers?

Simple addition — Erlang C for everything — gives you the wrong answer for async channels. Erlang C models a real-time queue: customers wait, agents must answer immediately. Email, tickets, and back-office work do not work that way. Items wait in a backlog; throughput is what matters, not queue dynamics.

Using one model for all channels can materially overstate or understate headcount — and operators lose trust in the plan. Each channel type gets its own honest model here.

Tower model vs. blended routing

The tower model treats each channel as a fully isolated silo. It is conservative and always safe — use it when agents are channel-dedicated, or when your routing platform does not support universal queues.

The blended estimatecalculates how much async work fits inside the idle gaps of your voice team (the time they are not on a call). This is the efficiency WFM managers call “blended routing” or “universal agent.” A typical voice team whose occupancy leaves genuine idle time — and whose routing platform supports blended work — can absorb some async workload before adding dedicated headcount.

Blended estimate is suppressed when voice occupancy ≥ 85% — no useful gap time remains above that threshold.

What each model does

• Voice — Erlang C: M/M/N queue formula. Computes agents required to hit a service level (e.g. 80% of calls answered within 20s).
• Email / tickets — Backlog flow: Required productive hours = (incoming × AHT + backlog reduction × AHT) / efficiency. Converts to FTE via paid hours and shrinkage.
• Back office — Productive hours: Same flow model as email. No queue, no service level — throughput and FTE are what matter.
• Chat — concurrency model: Live chat is staffed with a concurrency model based on sessions per interval, session duration, maximum simultaneous chats per agent, occupancy guardrail, and shrinkage. Chat is not absorbed into voice gap time in the blended estimate because it is synchronous work with first-response expectations.

Shrinkage in a multi-channel team

Shrinkage (breaks, training, sickness, admin) is applied independently per channel. In blended teams, the total shrinkage applied to the voice headcount effectively covers the async work handled in gaps — you do not double-count it.

If you run a shared shrinkage profile across all channels, set the same shrinkage percentage for each channel in this calculator. Use the shrinkage calculator to break it down by component first.