How Much Bandwidth Do I Need for VoIP?

VoIP and Bandwidth: The Basics

VoIP calls transmit voice as a continuous stream of data packets over your internet connection. The bandwidth required per call is modest — but it needs to be consistent and low-latency. Unlike a file download, where a brief interruption simply slows the transfer, a VoIP call is real-time. Even a short network disruption causes audible artefacts: echoes, choppy audio, or dropped calls.

How Much Bandwidth Does One VoIP Call Use?

The bandwidth used by a VoIP call depends on the audio codec employed. Common codecs and their bandwidth requirements:

• G.711 (standard quality): Approximately 80–90 kbps per call (each direction)
• G.722 (HD voice): Approximately 80–90 kbps per call — same bandwidth as G.711 but higher audio quality
• G.729 (compressed): Approximately 24–32 kbps per call — lower quality, used where bandwidth is constrained

Most business VoIP systems use G.711 or G.722 as the default codec. The 100 kbps per call figure is a safe planning assumption.

Calculating Your Business VoIP Bandwidth

Multiply your expected number of simultaneous calls by 100 kbps to get your VoIP bandwidth requirement:

• 5 concurrent calls: 500 kbps (0.5 Mbps)
• 10 concurrent calls: 1 Mbps
• 20 concurrent calls: 2 Mbps
• 50 concurrent calls: 5 Mbps

This is the bandwidth needed just for voice. Your total internet connection must also support all other business data: email, cloud applications, Microsoft 365, file transfers, and web browsing. As a rule of thumb, allocate at least double your VoIP requirement as headroom for other business traffic — preferably more.

Not Just Speed: Why Latency and Jitter Matter

Bandwidth is only one dimension of connection quality for VoIP. Two other parameters are equally important:

Latency

Latency is the delay between one party speaking and the other hearing them. For VoIP, latency below 150 milliseconds is generally imperceptible. Latency above 300 ms produces a noticeable delay that makes conversation awkward. Most business broadband connections in the UK have latency of 5–20 ms to the VoIP provider's servers — well within the acceptable range.

Jitter

Jitter is variation in packet arrival times. VoIP packets should arrive at regular intervals; variable timing causes choppy or robotic-sounding audio. A jitter buffer in the VoIP system compensates for minor jitter, but excessive jitter (above 30–50 ms) will degrade call quality noticeably. Jitter is more common on congested or poorly provisioned connections.

Choosing the Right Internet Connection for VoIP

FTTP (Full Fibre Broadband)

FTTP provides a direct fibre connection from the exchange to your premises. Download speeds typically 100 Mbps–1 Gbps; upload speeds proportionally high. Latency is low and consistent. For most SMEs with up to 20 concurrent VoIP calls, FTTP is adequate provided other data traffic is managed appropriately. Business FTTP typically costs £40–£80 per month.

Leased Line

A leased line provides a dedicated, uncontended connection with guaranteed symmetrical bandwidth and SLA-backed latency and uptime. For businesses where call quality is business-critical, or where VoIP is the primary communication medium across multiple sites, a leased line is the recommended solution. Leased lines start at around £69/month for a 100 Mbps connection.

FTTC (Fibre to the Cabinet)

FTTC uses fibre to the street cabinet and then copper from the cabinet to your premises. Performance degrades with distance from the cabinet. Upload speeds are typically 10–20 Mbps — adequate for modest VoIP use but can become constrained for businesses with 15+ concurrent calls. FTTC is being phased out in many areas as FTTP rollout expands.

Quality of Service (QoS) Configuration

Even with adequate bandwidth, VoIP quality can suffer if voice traffic competes with other data on a congested network. QoS configuration on your router prioritises VoIP packets over less time-sensitive traffic. This ensures that even during a large file upload or video conference, voice call quality is maintained. Most business-grade routers and managed switches support QoS — your IT provider or VoIP supplier can configure this as part of setup.

Testing Your Connection Before Migration

Before committing to a VoIP system, test your connection quality with a VoIP-specific tool. Tests at pingtest.net or your VoIP provider's test utility will show latency, jitter, and packet loss. Packet loss above 1% will noticeably degrade call quality; latency above 150 ms will cause perceptible delay. If tests reveal issues, address the underlying connectivity before deploying VoIP.