What is call center shrinkage? How to calculate it

Call center shrinkage is the share of the hours you pay agents for that they are not available to take calls. If you pay an agent for 40 hours a week and they are on the phones for 28 of them, shrinkage is 30%.

It is the number that turns a staffing formula into a real schedule, and it is the one most often forgotten. A forecast can be perfect and a call center still ends up understaffed every single interval, simply because nobody scheduled for the people who are in training, on a break or on holiday.

What is call center shrinkage?

Agents are paid for their whole shift, but they are not on calls for all of it. They take breaks, attend team meetings, sit in coaching sessions, go on leave, call in sick and wait while a headset or a system is fixed. Every hour that is paid but not spent available for calls is "shrunk" out of the time you can actually count on.

Shrinkage is always a percentage of paid time. That detail matters: unpaid lunch isn't part of paid time, so it doesn't count. Some teams call the same thing "off-phone time", but the idea is identical.

Why shrinkage matters for staffing

Staffing formulas such as Erlang C tell you how many agents you need logged in and taking calls. Shrinkage tells you how many people you have to put on the schedule to get them there.

If you need 11 agents on the phones and shrinkage is 30%, you schedule 11 ÷ 0.7 ≈ 16 agents. Skip that step, schedule 11, and on an average day you will have about eight on the phones. The queue grows, service level falls, and the agents who are there run flat out.

The shrinkage formula

The basic shrinkage formula is:

Shrinkage % = (paid hours − hours available for calls) ÷ paid hours × 100

Written the other way round, it is 1 minus the share of paid time agents are available. To use it in scheduling, divide the agents you need on the phones by what is left after shrinkage:

Agents to schedule = agents needed on the phones ÷ (1 − shrinkage)

Always round up. You cannot schedule 15.7 people.

A worked shrinkage calculation

Here is a full week for one agent who is paid for 40 hours, working five 8-hour days. Annual items are spread across 52 weeks.

Where the time goes	How it is worked out	Hours a week
Paid breaks	30 minutes a day × 5 days	2.5
Training	2 hours a week	2.0
Meetings and coaching	2 hours a week	2.0
Annual leave	20 days a year ÷ 52 × 8 hours	3.1
Sickness	6 days a year ÷ 52 × 8 hours	0.9
Public holidays	8 days a year ÷ 52 × 8 hours	1.2
Total		11.7

The shrinkage calculation takes three steps:

1. Convert everything to hours per week. Daily items are multiplied by the days worked; yearly items are divided by 52 and multiplied by the length of a working day.
2. Add the hours up. 11.7 hours in this example.
3. Divide by paid hours. 11.7 ÷ 40 = 29.3% shrinkage.

You can run your own figures through the shrinkage calculator, which also splits the result into in-office and out-of-office shrinkage.

In-office and out-of-office shrinkage

Split the total into two groups, because you manage them differently.

In-office shrinkage covers time the agent is at work but not on the phones: paid breaks, training, team meetings, coaching and system downtime. In the example above that is 6.5 hours, or 16.3%. You decide most of it, which means you can move it to quiet periods.

Out-of-office shrinkage covers time the agent is not there: annual leave, public holidays and sickness. In the example that is 5.2 hours, or 13.1%. Holidays and booked leave are known in advance. Sickness is not.

Item	Group	How much control you have
Paid breaks	In-office	Full: you set the break schedule
Training	In-office	High: schedule it in quiet intervals
Meetings and coaching	In-office	High: keep them short and well timed
System or headset downtime	In-office	Partial: fix the causes
Lateness and early finishes	In-office	Partial: manage adherence
Annual leave	Out-of-office	Medium: plan ahead and cap leave per interval
Public holidays	Out-of-office	None, but known well in advance
Sickness	Out-of-office	Low: add a buffer, tackle causes over time

Shrinkage vs absenteeism, attrition, occupancy and adherence

These terms get mixed up, and they measure different things.

• Shrinkage: the share of paid time that agents are unavailable, for any reason.
• Absenteeism: unplanned time off, mainly sickness. One input to shrinkage.
• Attrition: agents leaving the company. It affects headcount, not shrinkage.
• Occupancy: the share of logged-in time agents spend handling calls. It starts after shrinkage has taken its share.
• Adherence: how closely agents follow the schedule they were given. Poor adherence adds to in-office shrinkage.

How to schedule with shrinkage

Apply shrinkage to every interval, not once to the day. Calls come in waves, so the number of agents you need on the phones changes through the day, and each figure has to be divided by (1 − shrinkage) on its own. Here is a day with 30% shrinkage:

Interval	Agents needed on the phones	Agents to schedule
Quiet morning	6	9 (8.6 rounded up)
Busy mid-morning	11	16 (15.7 rounded up)
Peak after lunch	14	20
Late afternoon surge	20	29 (28.6 rounded up)

A flat extra 30% on top of the average would leave you short at the peaks and over-staffed in the quiet spells. The more of your in-office shrinkage you can place in quiet intervals, the lower your effective shrinkage at the peaks.

Shrinkage changes through the year

A single figure for the whole year hides a lot. Out-of-office shrinkage climbs in school holidays and around public holidays. In-office shrinkage jumps when you onboard a new group, run a training programme or roll out a new system. New agents also spend more time in coaching and shadowing, so a center with high turnover usually has higher in-office shrinkage than one with stable teams.

Recalculate for each season, and plan the busiest periods with the shrinkage you actually expect for them.

Where to get your own numbers

Use your own data, not a benchmark from another center.

• HR or leave system: annual leave, sickness and public holidays.
• Your ACD or dialer reports: time logged in, time available, and time in each "not ready" or auxiliary state (break, training, meeting, system issue).
• The training and coaching calendar: planned hours per agent.
• A few months of history, so one unusual week doesn't skew the figure. Calculate it per team if teams work differently.

Common mistakes

• Borrowing a number. A benchmark from another center says little about yours. Measure it.
• Counting unpaid lunch. It is not part of paid hours.
• Counting holidays twice. If you already schedule on working days, a public holiday isn't extra shrinkage.
• Treating it as fixed. In-office shrinkage is a choice. Plan it deliberately.
• Forgetting new starters. Agents in their first weeks spend more time in training and shadowing.
• Applying one flat figure to every interval. Do the sum per interval, as above.

How to bring shrinkage down

Look at the largest line first, and work on the part you control.

• Plan and cap leave ahead of time, so it is spread rather than bunched.
• Tackle the causes of short-term absence rather than just covering for it.
• Schedule training and meetings in quiet intervals, and keep them short.
• Fix recurring headset and system problems that keep agents off the phones.
• Tighten adherence, with clear schedules and a fair way to handle breaks that overrun.

Each point you take out is staff you no longer have to hire.

What to do next

Once you know your figure, put it into the Erlang C calculator to see agents on the phones and agents to schedule together. If your staffing numbers look off, check your average handle time too: it is the other big input.