Estimated reading time: 7 minutes
Key Takeaways
- Forecasting interval-level demand and understanding AHT are the foundations of accurate staffing.
- Use Erlang C or a trustworthy staffing calculator to translate workload into required advisers.
- Plan for occupancy in the 75–85% band to balance productivity and wellbeing.
- Always add shrinkage to move from “on-phone” to “scheduled” headcount.
- Design for peaks, not averages—coverage during high-traffic intervals protects service levels.
- Efficiency choices that cut AHT but lower FCR can backfire by driving repeat calls.
Table of contents
Understanding Staffing Basics
Determining the correct headcount for your call centre can make or break both customer experience and operational efficiency. Too few advisers create queues and disappointment. Too many push costs higher than they need to be. This guide explains, in plain language, how to work out the staffing level that fits your service goals.
Before running the maths, grasp the foundations of headcount planning. The task involves forecasting work, turning demand into workload, and translating that workload into agent numbers based on service levels and practical constraints.
Two elements steer nearly every staffing choice:
- Call volume forecasting. Predict how many contacts will land in each interval—commonly 15, 30, or 60 minutes—and note daily patterns and peaks.
- Average Handle Time (AHT). Add talk time, hold time, and after-call work. When you figure out AHT, leave shrinkage out and allow for variation between intervals.
“Forecast precisely, staff wisely, and your service levels will follow.”
Essential Calculators and Formulae
Customer Service Staffing Calculator
Web-based calculators turn volume, AHT, and service goals into headcount estimates. The newer ones also weigh abandon rates and caller patience.
Call Centre Staffing Formula
The standard approach uses the Erlang C model, which finds the probability of queuing when several advisers share the work. Feed the formula the following:
- Offered load in erlangs = (calls per interval × AHT in seconds) ÷ 3600
- Service level target, for example 80% of calls answered within 20 seconds
- Average speed of answer or target answer time
- Occupancy limits
Erlang C Calculator
An Erlang C calculator applies the model and returns either the adviser count needed for a chosen service level or, if you fix the adviser count, the service level you are likely to hit.
Step-by-Step Calculation
Here is a clear sequence that answers the question, “How many advisers do we need?”
- Forecast interval volume. Estimate calls in each 30-minute slice.
- Find AHT. Measure in seconds, adjust for queue type and time of day.
- Work out offered load. Use (volume × AHT) ÷ 3600.
- Set service targets. Many centres aim to answer 80% of calls inside 20 seconds.
- Run the numbers through an Erlang C or staffing calculator.
- Allow for reasonable occupancy. Continuous 100% occupancy burns advisers out, so plan for 75–85%.
- Add shrinkage. Turn on-phone full-time equivalents into scheduled full-time equivalents by folding in breaks, coaching, training, and meetings.
- Check peak intervals. Make sure high-traffic periods still meet the target.
Workforce Management Factors
Agent Occupancy
This shows the slice of paid time spent talking or finishing calls. Aim for 75–85% so productivity holds without harming wellbeing.
Shrinkage
Shrinkage covers paid time when advisers cannot answer calls.
Scheduled headcount = required on-phone advisers ÷ (1 – shrinkage rate)
Peak Demand
Plan for the busiest intervals rather than daily averages. Choose calculators that let you model peaks and lulls so you do not run short when demand surges.
Efficiency and Customer Experience
First Call Resolution (FCR)
FCR tracks the percentage of issues solved on the first try. Cutting AHT might look efficient, yet if it reduces FCR, repeat calls rise and staffing needs climb.
Balancing Team Size
To meet targets without wasting budget,
- Plan at interval level
- Use realistic occupancy bands
- Measure shrinkage with care
- Compare Erlang C output with simulation to keep estimates honest
Strategic Decisions
Adjusting Hiring
Watch for these signals and revisit your plan when they persist:
- Service level misses that persist
- Rising abandonment
- High occupancy over long stretches
- Extra volume from new channels
Outsourcing or In-House
Outsourcing can help in these cases:
- Peak-period cover
- Specialist support
- Longer opening hours
Weigh cost, control, and expertise before you choose.
Workforce Management Platforms
Modern platforms streamline staffing by blending Erlang-based planning, live forecasting, and automated rosters. Many include Erlang C calculators and multi-constraint models, giving sharper forecasts and day-of adjustments.
Conclusion
Working out how many advisers to schedule is not simple, yet it matters. Follow the steps in this guide—forecast demand, calculate offered load, use Erlang tools, add occupancy and shrinkage—and you will match resource to demand without harming experience. Apply the method often so it evolves with your centre. The right headcount keeps costs in line and customers content.
Further Reading
Explore these calculators to support your work:
- Assembled Erlang C explainer and calculator
- Bright Pattern staffing calculator that weighs service level, ASA, abandonment, and patience
- CallCenterCalculator.com for Erlang C versus simulation comparison
- Nelnet contact centre calculator, which factors in peak and off-peak traffic and business priorities
For more depth on forecasting and workforce planning, seek articles on Erlang C foundations, practical planning advice, and when simulation offers better precision.
Use the resources above alongside the principles in this guide and you will optimise staffing for efficiency and satisfaction.
FAQs
How do I convert forecast and AHT into the number of advisers?
Calculate offered load in erlangs using (contacts per interval × AHT in seconds) ÷ 3600, set your service target, then run an Erlang C calculator. Apply occupancy limits and add shrinkage to move from on-phone to scheduled headcount.
What is a good target for agent occupancy?
Plan for 75–85%. Below that you likely have excess capacity; above that, fatigue rises, quality dips, and small spikes can break your service levels.
How should I account for shrinkage?
Use scheduled headcount = required on-phone advisers ÷ (1 – shrinkage). Include breaks, meetings, coaching, training, holidays, and expected absence in your shrinkage rate.
Why does planning at interval level matter?
Demand is uneven. Interval-level planning ensures you staff to peaks and troughs rather than daily averages, protecting service levels when traffic surges.
Is cutting AHT always good?
No. If reducing AHT lowers first call resolution, you will see more repeat contacts and higher total workload. Balance AHT targets with quality and FCR.
When should I consider outsourcing?
Consider outsourcing for seasonal peaks, specialist queues, or extended hours. Validate partners on cost, quality controls, and how they support your service targets.
