Methodology

The exact formulas the calculator runs, and the reasoning behind each input.

The core formula

Required headcount is a comparison between two numbers: how many hours of work are arriving, and how many productive hours one agent actually delivers.

Required headcount = Total weekly workload hours ÷ Productive hours per agent

The result is rounded up, since a fraction of a person is still a whole shift you need to cover.

Step 1 — Workload hours

Workload is volume multiplied by average handle time (AHT), converted to hours:

Workload hours = (Weekly volume × AHT in minutes) ÷ 60

AHT can be entered in seconds, minutes, or hours in the calculator — it's converted to minutes internally before this step.

Step 2 — Paid hours per agent

This is simply the agent's schedule:

Paid hours per agent = Shift length (hours/day) × Days per week

Step 3 — Shrinkage

Shrinkage is the portion of paid time that isn't available for handling work. The calculator breaks it into four components:

Vacation & holidays — entered as days per year, then averaged across 52 weeks and converted to a percentage of weekly paid hours.
Sick & unplanned leave — same annualized treatment as vacation.
Training & meetings — entered directly as hours per week (or as a percentage), since these tend to recur on a weekly cadence rather than an annual one.
Breaks & short idle time — same weekly treatment as training.

The four components sum to a total shrinkage percentage. If you'd rather skip the breakdown, the calculator's "Quick total" mode lets you enter one combined shrinkage percentage instead.

Available hours per agent = Paid hours × (1 − Total shrinkage %)

Step 4 — Occupancy

Occupancy is the share of available time (after shrinkage) that's actually spent handling work, as opposed to waiting for the next item. A 100% occupancy target assumes agents are handling something every second they're available, which isn't realistic or sustainable — most operations target somewhere between 75% and 90%.

Productive hours per agent = Available hours × Occupancy target %

Putting it together

Required headcount = ⌈ Workload hours ÷ Productive hours per agent ⌉

Reverse mode: capacity from headcount

The same relationship runs in the other direction. Given a fixed number of FTEs, multiply by productive hours per agent to get total weekly capacity in hours, then convert back to volume using AHT:

Max weekly volume = (FTE count × Productive hours per agent × 60) ÷ AHT in minutes

What this model doesn't do

This is a steady-state average model — it answers "how many people, on average, across a week." It does not account for:

Intraday or interval-level arrival patterns (peaks within a day)
Queueing behavior or service-level targets (the kind of math an Erlang C calculator handles)
Multi-skill routing or cross-trained agent pools
Ramp-up time for new hires

It's built for headcount and budget planning at a weekly or longer horizon — not for building an interval-by-interval shift schedule.

Open the calculator →