3CX is licensed by simultaneous calls (SC) — how many conversations happen at the same time — not by how many people work for you. This is what makes it cheaper than per-user systems, and it is also the number most people get wrong.
Count calls, not employees
Internal calls count too. A call between two of your own extensions uses one simultaneous call.
As a rule of thumb, an ordinary office needs roughly one simultaneous call for every four to six people. A sales or support team on the phone all day needs far more; a warehouse or workshop needs far less.
3CX recommended ranges
| Licence | Maximum extensions | Recommended team size |
|---|---|---|
| 8 SC | 40 | 16–40 |
| 16 SC | 80 | 41–80 |
| 24 SC | 120 | 81–120 |
| 32 SC | 192 | 121–192 |
| 48 SC | 288 | 193–288 |
A company of 40 people therefore sits at the top of an 8 SC licence — comfortable for a mixed office, tight if most of those 40 are on calls at once.
How do I know I have outgrown my licence?
The symptom is callers hearing a busy tone or being sent to voicemail while extensions are still free. That means every simultaneous-call slot is in use.
Upgrading
Upgrades are handled from your client area, or by opening a ticket with us. You keep your extensions, numbers and configuration — only the licence capacity changes. Billing is adjusted pro rata for the remainder of your term.
See all plans and capacities, or compare the BASIC, PRO and AI editions.