Why is the FTE figure higher than volume ÷ handle time would suggest?

Three reasons, all visible in the table: Erlang C needs agents above the workload to keep queues short, the occupancy ceiling adds more for small intervals, and shrinkage grosses the whole curve up. Then roster efficiency adds the hours that shifts leave in the troughs. Each is a real cost; a simple workload sum is the number you will be under-staffed by.

Which shape should I pick?

Look at an hourly volume report. Most inbound consumer lines are double-peaked with a lunch dip; business-to-business lines are often single-peaked in the morning; evening-heavy suits retail and utilities. If you have the intervals, paste them and skip the guess.

Does this handle different days of the week?

Yes. The day-of-week split gives each day its share of the week, and each day runs its own curve, so a Monday that is 30 per cent heavier than Thursday gets 30 per cent more contacts in every interval and its own peak. The FTE sums every day's agent-hours. Set a day to zero to close it. What it does not do is change the shape of the day between weekdays; a workforce management tool does that from the forecast.

What roster efficiency should I use?

Measure it from a current roster with the schedule efficiency calculator: required hours ÷ rostered hours. 85 to 95 per cent is typical. If you do not have one, 90 per cent is a fair planning assumption for a centre with some part-time or flexible shifts, and lower for one built on identical full-time shifts.

Week planner and FTE calculator

One interval tells you how many agents you need at eleven o'clock. This planner runs the full staffing chain for every interval of a typical day, from a daily, weekly or monthly volume spread across your opening hours, or from interval volumes you paste in. It charts the requirement, sums the agent-hours, and converts them to FTE.

Inputs

Requirement curve

FTE at roster efficiency

65.9

90% of rostered hours land on the curve.

On the phones
Shrinkage allowance

Theoretical FTE: 59.3
Agent-hours per week: 2,225.0 h
Agent-hours per day: 445.0 h
Peak interval: 53 at 11:00
Average scheduled: 37.1
Contacts per day: 3,000

Show the working

3000 contacts per day is the average open day: 15000 a week across 5 open days, spread over 8:00 to 20:00 in 30-minute intervals using the "Morning and afternoon peaks" shape.
The day-of-week split is even, so every open day carries 3000 contacts.
Each interval runs Erlang C for 80% within 20 s, adds agents until occupancy is at or below 85%, then divides by (1 − 30%) and rounds up.
Mon's peak is 11:00: 187 contacts need 37 on the phones and 53 scheduled.
Agent-hours per day = Σ scheduled × 30 ÷ 60 = 445.0 h; × 5 days = 2225.0 h a week.
FTE = 2225.0 ÷ 37.5 contracted hours = 59.3. Shrinkage is already in the per-interval numbers, so contracted hours are the right divisor.
At 90% roster efficiency, 59.3 ÷ 0.90 = 65.9 FTE to cover the curve with real shifts.

This is one typical day. Pebble WFM does every day from your forecast, then builds and publishes the roster. Free month, no card needed.

How the planner works

The volume you enter is converted to a week: a daily figure is the average open day, a monthly figure is first converted to a week (× 12 ÷ 52). The week is divided across the days you are open using the day-of-week split, and each day is spread across your opening hours using the shape you pick, or the interval volumes you paste, which can come straight from an ACD report.

Every interval runs the staffing requirement chain: Erlang C for the service level target, the occupancy ceiling, then shrinkage. That gives agents on the phones and agents to schedule for each interval, and the chart is the requirement curve a roster has to cover.

Agent-hours a day is the sum of scheduled agents × interval length, and the week is the sum over open days. Dividing by contracted hours per FTE gives the theoretical FTE. Shrinkage is already in the per-interval numbers, so contracted hours are the right divisor; using productive hours here would count shrinkage twice. Roster efficiency then allows for the fact that shifts never fit the curve exactly.

Read the full guide: How to calculate FTE from contact volume

Frequently asked questions

Why is the FTE figure higher than volume ÷ handle time would suggest?: Three reasons, all visible in the table: Erlang C needs agents above the workload to keep queues short, the occupancy ceiling adds more for small intervals, and shrinkage grosses the whole curve up. Then roster efficiency adds the hours that shifts leave in the troughs. Each is a real cost; a simple workload sum is the number you will be under-staffed by.
Which shape should I pick?: Look at an hourly volume report. Most inbound consumer lines are double-peaked with a lunch dip; business-to-business lines are often single-peaked in the morning; evening-heavy suits retail and utilities. If you have the intervals, paste them and skip the guess.
Does this handle different days of the week?: Yes. The day-of-week split gives each day its share of the week, and each day runs its own curve, so a Monday that is 30 per cent heavier than Thursday gets 30 per cent more contacts in every interval and its own peak. The FTE sums every day's agent-hours. Set a day to zero to close it. What it does not do is change the shape of the day between weekdays; a workforce management tool does that from the forecast.
What roster efficiency should I use?: Measure it from a current roster with the schedule efficiency calculator: required hours ÷ rostered hours. 85 to 95 per cent is typical. If you do not have one, 90 per cent is a fair planning assumption for a centre with some part-time or flexible shifts, and lower for one built on identical full-time shifts.

Stop doing this one interval at a time

Pebble WFM forecasts your demand, computes the staffing requirement for every interval, builds the roster and publishes it, with self-service for agents and a copilot that can do what a planner can. Explore a sample organisation on day one.

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