Telephone Capacity Calculation

There are a number of resources which practices could use to calculate the capacity required to ensure good telephone response. The following Links direct you to these resources.

These are external links which the Foundation has no control or influence on.

The Danish mathematician Agner Krarup Erlang – an expert in telephone systems – devised the standard formula used for calculating the maximum number of calls per hour that can be handled by a given number of agents (receptionists/call-handlers) given an average call length and the service level that is desired.  We have provided below some links to resources that are available on the web.  We do not provide any guarantee or recommendation for any of the sites and you will find others by searching for Erlang calculators, but we hope that these are useful to you.

Link 1.  Department of Mathematics, Amsterdam University.  This takes you to an on-line calculator that will calculate the service level.  Fill in the average call volume for an hour (arrivals), the average length of the call (service time) and the number of staff devoted to answering the phones (number of agents).  We also recommend that you fill in the bottom right box with 30 seconds so as to calculate the percentage of calls that will be answered in 30 seconds – as a guide the National standard for out of hours services is that 95% of calls should be answered in 30 seconds, a value below 90% in 30 seconds is generally thought unacceptable by telephone call-centre experts.

Link 2 and 3.  Free add-ins for excel. This add-in will allow the calculation of service level given a number of agents or the number of agents required to deliver a particular service level and you can build the formulae into an excel model.  Alternatively there is a free calculator provided by call centre at

Link 4.  There is a freeware version of cc-modeler professional known as cc-modeler lite at http:www.kooltoolz.comccm.htmgclid=CJbU1vm8vZQCFQKaFQod1ChLTg
Again this will allow the calculation of service level given a certain number of agents or the calculation of the number of agents needed to deliver a particular service level.

Link 5.  For the mathematically minded the formulae are provided at:  Here they also describe how the various formulae can be written into excel.
Link 6.  Wikipedia provides an overall description of the Erlang formula and what it does at:

About Us

The Primary Care Foundation was established to support the development of best practice in primary and urgent care.  The three Directors bring different skills and perspectives to understanding primary and urgent health care - for more details click below:

David Carson

Rick Stern

Henry Clay



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New on-line registration for the potentially avoidable appointments audit

The Primary Care Foundation were selected by NHS England to further improve and automate the audit of potentially avoidable appointments. We are now building a new website with Method Analytics that will make it much easier for any practice to register online, will simplify data collection for clinicians, and will allow for instant reporting on results. The reports will be much easier to understand and will signpost other support. And it will remain free to use for all practices in England.

We are now ready to go live with a new ‘test’ site. We are confident it is already easier to use but we are keen to get any feedback from practices before the new website is fully up and running.

If you are a practice in England and you want to register, CLICK HERE  and click on ‘register here to create a practice audit!’ You will be guided through registration and how to set up your clinicians to take part in the audit.  This is a new test site, so if you notice anything that doesn’t look right, or could be made easier, just let us know.  And the same for your clinicians as they enter data – any feedback at the moment – good or bad – would be really helpful … just email us This email address is being protected from spambots. You need JavaScript enabled to view it.


What do we mean by an ‘avoidable appointment?

The latest blog by Rick Stern ‘If only …’ explores the idea of avoidable appointments, what practices have gained from the audit, and what might be possible with further investment in general practice. It is available HERE and will also be published in Health Care Leader.


Are there any simple lessons for practices looking to improve access?

A feature article in Management in Practice by Rick Stern reviews what we have learned from working with over 1,500 practices across the UK – you can read the full article HERE  


Integrated Urgent Care – how to make NHS 111 work

A lead article for Health Care Leader by Henry Clay describes a financial and capacity model developed for NHS England, the potential benefits and pitfalls, and what we have learned from working with a dozen areas to apply the model. The article is available at HERE and a fuller version with a number of explanatory graphs can be downloaded HERE


Integrated Urgent Care – opportunity for support to your locality

We have developed a financial model for the Integrated Urgent Care Team at NHS England that focuses on the NHS 111 and OOH ‘front end’ to an integrated urgent care system (but also looks at the cost of onward referrals to other services). This is proving to be an invaluable tool for both commissioners and providers. It is now available to use and NHS England have also agreed to support some sites to setup and work through the model with PCF’s Henry Clay who developed the model. For further information please contact Henry on This email address is being protected from spambots. You need JavaScript enabled to view it.


We are now supporting over 1,500 practices across the UK to manage access and urgent care

Our support for general practices looking to improve access for patients and streamline the management of urgent care continues to expand. Based on a web based tool, developed out of our work commissioned by the Department of Health, we collect practice data for one week and prepare a report for each practice looking at how you compare to others and explore what this means for making practical changes in the way you work. We are regularly improving the format of our reports for practices based on constant feedback. If you would like to see an example report, CLICK HERE.  If you want to know more about how we might work with you please contact Rick Stern on  This email address is being protected from spambots. You need JavaScript enabled to view it.  or call on 07709 746771.