How to calculate size of IT department

People occupying managing positions may have difficulties while calculating amount of IT employee required for their organization. At the same time, they are not sure if they can trust demands coming from heads of IT departments. The intention of this writing is to show clear and transparent way how IT staff can be estimated.

Work of IT department can be divided into two big parts: work with people, which is mostly user support and work with IT infrastructure, such as network wiring, network equipment, servers and so on. So, let’s look to both parts.

1. Amount of IT areas to one person.

It's known from the psychology, individual can equally distribute and support attention among 6 - 11 objects at a time, depending on its possibilities. Assuming, IT work by head (and train it), lets take 10 - close to upper border. By the way, that's the reason why, smallest army unit is usually 10 people: 9 soldiers plus a commander. If there would be more, commander would loose ability to effectively manage the unit.

Each IT area has, at least 3 key (big) fields to follow. This is true for all technical disciplines. For example, modern VoIP PBX. Three key fields are: network environment, telephony environment and internal programming. Another, not very technical example, for those who are quite far from understanding what VoIP PBX abbreviations mean, could be a driver driving a car. To reach the point of the destination, he should have three areas under attention. The driver must watch the situation on the road, manage driving controls and follow the route to the destination in his head or on navigator panel.

In its turn, those fields consist of other components and so on.

So, 10 objects of attention for individual and 3 key fields of attention in each technical area means we can assign 10 / 3 = 3 and 1/3 or approx. 3,33 IT tasks to a person or to one FTE.

In practice, ideally, is to assign 3 IT areas to a person. 4 is ok, but not brilliant as 4 x 3 = 12 fields of attention. Maximum maximorum is – 5 IT areas. Expansion beyond this border leads to the situation when IT tasks will suffer from extreme degradation of performance or quality.

In case of 5 IT areas assigned to an IT FTE - we get 5 x 3 = 15 fields requiring attention.

That calculation fully corresponds to the practice of real life.

This means - more unique (by functionality) systems we have, or IT areas of activities - more people we need. Examples: 30 routers of 'Cisco 2900' model - is still one IT area. 1 mail server, 1 FTP server, 1 VPN server - are 3 IT areas.

IT area is a direction of attention. If the organization is highly using Debian linux in its environment, Debian linux should be considered as an IT area. So, IT area can be a concrete thing as a router of certain type such as 'Cisco 2900', or wide, intensively used area of skills and knowledge, which we could indicate in a list as 'Debian Linux', or 'VoIP technologies', or 'SAMBA'.

From this, we can derive a practical formula. 1 IT FTE per 3 - 4 IT areas.

2. User support

Normal adopted by IT world practice is - 1 IT FTE per 50 users or work seats.

3. Example of calculations

IT areas, used in a Company:

1. Cisco Call Center

2. Cisco Routers

3. Debian Linux – used on most servers, some VPN routers and for many other purposes

4. Linux based RAID – used on every server

5. Open Source based e-mail solution

6. Freeswitch – free VoIP call platform/PBX

7. Network design – area requiring constant attention

8. VoIP hardphones/softphones

9. Ethernet switches

10. DNS Server

11. FTP server

12. DHCP server

13. TTS server

14. Voice recording server

15. SAMBA file server

16. Conference server

17. User PC (software, hardware installation)

18. Jumis, Solcraft – Bookkeeping solution

19. WEB server

20. Helpdesk, task ticketing

21. Virtualization

22. tinc VPN

23. Linux HA,

24. Linux security/firewall

25. Development for linux networking (Spain, Ukrain) – special development project for newly opening offices

26. Development for FreeSWITCH – Open source VoIP platform may require development of many things to suite needs of the company

27. Telephony design

28. VoxBone

29. DIDWW

30. Strategic planning and control

31. Operational planning and control

Amount of occupied user workplaces: 105

Total IT FTE: 31  (IT areas) divided by 4 (max IT areas to one person) + 105 (occupied user workplaces) divided by 50 (work seats per FTE) = 31/4 + 105/50 = 9.85 FTE

Total of optimally loaded FTE: 31/3 + 105/50 = 12.4 FTE

Total of max loaded FTE: 31/5 + 105/50 = 8.3 FTE

Please also take into account, people may have a wish to go to vocations some times and there should be replacing persons for such situations.