Hotline and Call Centre Staffing Calculator (Erlang C)

How many people does a health hotline or call centre need? Enter your busiest hour and service target to get the agents needed, the agents to schedule and the average wait, using the Erlang C model. Load a program example, from public health to business, to see how it changes.

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Example

Calls in the busiest hour Average handle time (minutes) talk plus wrap-up Service level target (%) share of calls answered within the time below Answer within (seconds) Shrinkage (%) breaks, training, absence

Agents on the phones-

Agents to schedule-

Average wait-

Occupancy-

FormulaTraffic A = calls per hour × handle time (hours) · Erlang C: P(wait) for N agents · Service level = 1 − P(wait) × e^{−(N − A) × t ÷ AHT}

What to do next

Show the working, step by step

Where I used this

Through Praava Health’s partnership with Lifebuoy, we took health access to population scale, with about 3,000 calls a day.

Read the case: Population-scale access via the Lifebuoy partnership →

Step beforeWho you must reach: Coverage gap Next stepPlain words on the line: Health message readability Business twinCost of the channel: CAC by channel

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Why staffing a hotline is not simple division

Calls do not arrive evenly. Dividing talk time by 60 minutes gives the absolute minimum, and a hotline staffed at that level will have long queues. The Erlang C model, the standard method in call-centre planning, accounts for random arrivals and tells you how many agents it takes to answer a chosen share of calls quickly.

I used the same thinking when standing up a population-scale health hotline handling around 3,000 calls a day. A few practical lessons:

Plan for the busiest hour, not the daily average. Health hotlines spike after campaigns, news and outbreaks.
Keep occupancy below about 85%. Above that, agents have no breathing room and quality falls, which matters when callers are worried or unwell.
Shorter is not always better. Cutting handle time by rushing callers can push repeat calls up. Clear scripts and good triage are the real lever.

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Planning a health hotline?

Bring your call volumes to a free 30-minute call. Through Praava Health’s partnership with Lifebuoy we handled about 3,000 calls a day, and I will help you staff for the peak.

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Questions

What is Erlang C?

A queueing formula that estimates the probability a caller has to wait, given how many calls arrive and how long they last. It is the standard way to size call centres and hotlines.

What is a typical service level target?

80% of calls answered within 20 seconds is a widely used benchmark. Crisis and emergency lines usually aim higher.

What is shrinkage?

The share of paid time agents are not available to take calls: breaks, training, meetings, sickness and leave. 25% to 35% is common.

Hotline staffing calculator