How many lines and seats do you need
How to size both from your own call records, and the ratio that stops you buying a line for every person.
What is the difference between a line and a seat?
A seat is a person with their own extension and voicemail. A line is one call happening at once. You need a seat for everyone who answers the phone, but only enough lines to cover the busiest moment of the day. Confusing the two is the most common way businesses overpay.
How many lines
| Type of business | Rough ratio | Example |
|---|---|---|
| Office where calls are occasional | 1 line per 4–5 people | 20 staff, around 4–5 lines |
| Sales or service team on the phone often | 1 line per 2–3 people | 20 staff, around 8 lines |
| Support desk or contact center | Close to 1 line per person | 20 agents, 18–20 lines |
| Retail or trade counter | 2–4 lines regardless of headcount | Calls are short and bursty |
Work it out from your bill
Pull last month from your current provider
Ask for call detail records. Most will send them if you ask.
Find the busiest hour
Usually mid-morning. Count how many calls overlapped at the peak.
Add one or two
Enough for a quiet margin without paying for a peak that happens twice a year.
Ask what happens when you exceed it
Some systems send the extra caller to voicemail, others let you burst and bill it. Very different outcomes.
How many seats
Count everyone who needs their own number, extension or voicemail. A warehouse phone, a meeting room or a lobby handset is usually a cheaper common seat rather than a full one. The difference over a three-year term is significant.
Easy ways to overpay
- Buying a seat for every employee instead of every phone user
- Keeping lines for departments that no longer exist
- Paying for unlimited minutes when your usage is modest — check the actual minutes on your bill
- A handset on every desk when most staff work from an app
Last reviewed September 14, 2026
