Work out how much paid agent time goes to breaks, meetings, training, admin and leave, and how many agents to roster to keep the number you need on the phones.
Already know your shrinkage? Enter it in the Erlang C calculator to size agents, then cost the team with the call center cost calculator.
The paid shift, including breaks. Decimals are fine: 8.5 is eight and a half hours.
Paid time on shift when the agent is not taking calls. Use your own averages.
Paid breaks and lunch, if lunch is paid.
Average per day: a 1-hour weekly session on a 5-day week is 12 min.
Logins, outages, emails and other off-phone work.
Share of rostered agent-days lost to planned leave, sick leave and unplanned absence.
From your Erlang C or forecast. Leave at 0 to skip the roster count.
Total shrinkage
28.0%
1 - (1 - internal) x (1 - absence)
Internal shrinkage
20.0%
96 of 480 paid minutes
Absence shrinkage
10.0%
Rostered days lost
Simple sum (for comparison)
30.0%
Internal + absence, double counts
Agents to roster
28
for 20 on the phones, rounded up
Productive hours on a working day
6.4 h
Paid hours less internal shrinkage
Productive hours per rostered day
5.76 h
Averaged over leave and absence
Worked out: 1 - (1 - 0.200) x (1 - 0.100) = 28.0%. Adding the two gives 30.0%, which counts the breaks an absent agent would never have taken.
Roster 28 agents so that, after breaks, meetings, training and absence, about 20 are taking calls. That is 8 agents of cover for shrinkage.
Using the simple sum instead would roster 29, 1 more than you need.
Assumptions
Use your shrinkage there: enter the total shrinkage above in the Erlang C calculator to turn agents on the phones into agents to schedule, then price the roster with the call center cost calculator.
Shrinkage hits hardest in the busy hours. An AI voice agent can answer overflow and after-hours calls in Indian languages, book into Google Calendar and hand off to your team, so you roster for the normal day, not the worst hour.
Talk to us about a voice agentShrinkage is the share of paid agent time when agents are not available to take calls. It has two parts.
Total shrinkage = 1 - (1 - internal) x (1 - absence)
With 20% internal and 10% absence: 1 - 0.80 x 0.90 = 1 - 0.72 = 28%.
Many teams add the two instead (20% + 10% = 30%). That double counts: an agent on leave takes no breaks and attends no training that day, so the internal minutes only apply to the 90% of agents who turn up. Multiplying applies each loss to the time that is actually left. The simple sum comes out higher whenever both parts are above 0, so it over-rosters slightly, and the gap grows as either part grows.
Agents to roster = agents needed on the phones / (1 - total shrinkage), rounded up. If Erlang C says 20 agents must be taking calls and shrinkage is 28%, roster 20 / 0.72 = 27.8, so 28 agents.
Plan by interval where you can. Breaks and meetings cluster at certain times, so a daily average can hide a short gap at a busy hour.
Benchmarks vary widely by centre, shift pattern, country and how each centre defines shrinkage. Build the figure from your own WFM or attendance data rather than a published average, and recheck it every few months.
When shrinkage leaves the busy hour short, an AI voice agent can take the overflow, answer after hours and hand complex calls to your agents. It speaks Indian languages with a regional tone, books into Google Calendar and posts to Slack or Teams. Try Edesy Voice Agent or talk to us about a voice agent.
Comparing costs first? Read AI vs human call center cost in India.
Shrinkage is the share of paid agent time when agents are not available to take calls. It covers on-shift time such as breaks, meetings, coaching, training and admin (internal shrinkage), and days lost to leave and absence (external shrinkage).
Internal shrinkage = off-phone minutes on shift / paid minutes. Total shrinkage = 1 - (1 - internal) x (1 - absence). For 20% internal and 10% absence, that is 1 - 0.8 x 0.9 = 28%.
Adding them double counts. An absent agent takes no breaks or training that day, so internal shrinkage only applies to the agents who are at work. The simple sum is always a little higher than the combined figure and leads to slightly too many agents on the roster. The calculator shows both so you can compare.
Divide the agents you need on the phones by (1 - total shrinkage) and round up. For 20 agents on the phones at 28% shrinkage, that is 20 / 0.72 = 27.8, so 28 agents.
There is no single right figure. Benchmarks vary widely by centre, shift length, training load and how shrinkage is defined. Use your own attendance and WFM data, and track the trend over time.
Use your shrinkage there. Erlang C works out how many agents must be on the phones for your service level, and the Erlang C calculator takes shrinkage as an input to turn that into agents to schedule. Enter the total shrinkage from this page.
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Internal, absence and total shrinkage
Shows the formula with your numbers
Simple sum shown for comparison
Productive hours per agent per day
Agents to roster, rounded up
Runs in your browser, no signup
Turn the agents an Erlang C model says you need on the phones into the headcount to schedule.
See how much a new weekly training block or a rise in sick leave adds to headcount.
Rebuild a shrinkage number from its parts and see whether it was added or combined correctly.
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