What internet speed do I need for VoIP?

How much bandwidth does a single VoIP call use?

A standard VoIP call sends compressed audio in small data packets. The widely used G.711 codec runs at about 87 kbps once you add the network overhead, and the lighter G.729 codec uses around 30 kbps. HD voice codecs such as G.722 sit in a similar range to G.711 but sound clearer. To keep the maths simple and leave headroom, plan for about 100 kbps per concurrent call in each direction.

That is genuinely small. A single call uses roughly the same data as streaming low-quality audio, and works out at about 1 MB per minute. The key word is "concurrent". You are not paying bandwidth for every handset you own, only for the calls happening at the same time. Most businesses have far fewer simultaneous calls than total staff, because not everyone is on the phone at once.

Voice is also two-way, so you need that 100 kbps going out as well as coming in. This is why upload speed is the figure to check first. Older connections often have generous download but limited upload, and your callers hear the problem if your upload runs out.

What internet speed do I need by team size?

The table below shows recommended spare bandwidth by the number of calls happening at once. We assume about 100 kbps per call each way, then add comfortable headroom so backups, email and browsing do not interfere. These figures are for voice only and sit on top of your normal internet use.

Simultaneous calls	Typical team size	Minimum spare upload & download	Comfortable line to have
1 to 2	Sole trader or 2 to 5 staff	~0.2 Mbps each way	Any FTTC or fibre line
3 to 5	Small office, 5 to 15 staff	~0.5 Mbps each way	FTTC 40/10 or SoGEA
6 to 10	15 to 30 staff	~1 Mbps each way	SoGEA or entry FTTP
11 to 25	30 to 60 staff	~2.5 Mbps each way	FTTP 100 Mbps or better
25 to 50	Larger office or busy contact team	~5 Mbps each way	FTTP with symmetric upload

As you can see, even a busy office with 25 calls running at once needs only about 5 Mbps of spare bandwidth in each direction. The reason businesses still buy faster lines is everything else: cloud apps, video calls, file sync and a margin for growth. Voice itself is light. If you want a wider view of how calls become data, see our guide to what VoIP is and how it works.

Which UK connection type is best for VoIP?

For business VoIP in the UK, full-fibre FTTP (fibre to the premises) is the best choice where it is available. It offers high upload speeds, low latency and, on many packages, symmetric speeds where upload matches download. That headroom keeps voice clear even when the office is busy with other traffic.

Where FTTP has not reached yet, SoGEA is the next best thing. SoGEA is fibre to the cabinet that has dropped the old analogue phone line, so you get broadband without paying for a line you no longer need. Both FTTP and SoGEA are well suited to the PSTN switch-off in January 2027, because they carry voice over the internet rather than the legacy network that is being retired.

Standard FTTC (fibre to the cabinet) still works perfectly well for smaller teams. A common 40/10 package, meaning 40 Mbps down and 10 Mbps up, handles dozens of concurrent calls. The thing to avoid is relying solely on a single mobile-data connection for a busy office, although 4G or 5G makes an excellent backup line.

Why do calls sound bad even on a fast connection?

If your broadband is quick but calls still drop out, the problem is rarely raw speed. Three things affect call quality far more than download figures: latency, jitter and packet loss. Latency is the delay before audio arrives, jitter is the variation in that delay, and packet loss is the small chunks of audio that never turn up. Any of them makes calls sound robotic, clipped or echoey.

The usual cause is contention on your upload. A large file upload, a cloud backup or several video meetings can flood your outbound connection and starve voice packets. The fix is Quality of Service (QoS), a setting in most business routers that gives voice traffic priority over everything else. With QoS on, a backup running in the background no longer ruins a sales call.

A few practical tips help: use a wired connection for desk phones where possible, keep your router firmware up to date, and place Wi-Fi access points well if staff use the softphone or mobile app. If problems persist, your provider can run diagnostics on the call data. For what happens when the connection drops entirely, read our guide to VoIP in a power cut or internet outage, and compare the technologies in VoIP versus landline.