How Much Bandwidth Does VoIP Need?

Last checked: 19 October 2026

A single VoIP call typically needs somewhere between about 30kbps and 140kbps in each direction, depending on the codec and the provider. Virgin Media O2 Business, for example, says its Cloud Voice service typically needs 140kbps per concurrent call. To size your connection, multiply the per-call figure by the most calls you will have at the same time, then check your upload speed as well as your download speed, and leave headroom for everything else on the line.

Voice uses very little bandwidth compared with video or file transfers. Most VoIP quality problems come from a connection that is busy, unstable or poorly configured, not from a lack of raw speed. This guide shows how to work out what you need and what else to check.

How much bandwidth does one VoIP call use?

The figure depends on the codec (how the voice is compressed) and the overhead added by the network. Here are published figures from equipment and service providers:

The spread is normal. A codec's headline rate (64kbps for G.711, for example) is only the voice itself. Each packet also carries addressing and transport headers, which is why Cisco's Ethernet figure for G.711 is 87.2kbps rather than 64kbps. Providers then add their own margin. If your provider publishes a figure, use theirs: it reflects the codecs their system actually uses.

Does VoIP use upload or download bandwidth?

Both. A call sends your voice out and brings the other person's voice in at the same time, so you need the per-call figure in each direction. Microsoft's Teams table, for example, is written as "up/down".

This matters because business broadband is usually asymmetric. A connection with plenty of download speed can still run short on upload, especially when cloud backups or large file uploads are running at the same time as calls.

How do I work out how many concurrent calls I need?

Bandwidth depends on how many calls are happening at once, not how many phones you have. Virgin Media O2 Business suggests a simple rule of thumb:

• Busy phone teams (sales, support, bookings): assume one concurrent call per user.
• Offices where calls are infrequent: assume roughly a third of users on calls at once.

Then use this calculation:

Peak concurrent calls × bandwidth per call = minimum bandwidth for voice, in each direction

Add any other real-time traffic that happens at the same time, such as video meetings, then leave headroom for normal internet use.

Worked example: an 18-person office

Suppose you have 18 staff on a hosted phone system. Six work in a busy customer service team and the other 12 make occasional calls. You plan for up to three video meetings at once.

1. Customer service team: 6 users × 1 concurrent call each = 6 calls.
2. Rest of the office: 12 users ÷ 3 = 4 calls.
3. Peak concurrent calls: 6 + 4 = 10 calls.
4. Voice bandwidth: 10 calls × 140kbps = 1,400kbps, or about 1.4Mbps in each direction.
5. Video meetings: Microsoft recommends 1,500kbps up and down for a one-to-one Teams video call. Three at once is about 4.5Mbps in each direction.
6. Real-time total: about 5.9Mbps upload and download at the busiest moment.

On a typical SOGEA business broadband connection, such as the Sky Business Broadband SOGEA service we supply at up to 80Mbps download and 20Mbps upload, that leaves room for everyday use, provided nothing else saturates the upload. A large cloud backup running during the working day could, so schedule it out of hours or prioritise voice traffic (see below).

If the office had a single upload-heavy workload running all day, such as video production or large drawing files, the answer might be a faster upload service such as full fibre or a leased line. Our guide to leased line vs full fibre compares the two.

Is speed the only thing that matters?

No. Voice is sensitive to the quality of the connection as much as its size. Microsoft's Teams guidance notes that calls which "have static and cut out, or voices sound like robots" could be caused by jitter or packet loss, rather than bandwidth. Things to check:

• A stable connection. Run several speed tests at your busiest time of day, not just one first thing in the morning.
• Quality of Service (QoS). Microsoft recommends using QoS to prioritise voice traffic, noting that even a network with enough bandwidth benefits when unexpected traffic spikes occur. Ask your provider whether the router they supply can prioritise voice.
• VPNs. Microsoft recommends letting Teams traffic bypass the VPN where possible (split tunnelling), because VPNs are not usually designed for real-time media and can add latency and jitter. The same principle applies to other VoIP services; check your provider's guidance.
• Wi-Fi. Microsoft notes that Wi-Fi networks are not necessarily designed for real-time media, and suggests the 5GHz band and prioritisation (QoS or WMM) where you rely on wireless. Wired desk phones avoid the issue entirely.
• A provider network test. Many providers test your connection before installation. BT, for example, says you must pass its network assessment test, which checks your local network, broadband connection and VoIP service, before you can order BT Cloud Voice.

What broadband do I need for VoIP?

There is no single answer, but this is a practical way to decide:

If you are moving from an old phone system, our hosted VoIP guide and SIP trunking vs hosted VoIP comparison explain the options.

Frequently asked questions

How many VoIP calls can 1Mbps handle?

It depends on the per-call figure. At Virgin Media O2's typical 140kbps, 1Mbps (1,000kbps) covers about 7 calls in each direction. At Cisco's 87.2kbps G.711 figure it covers about 11, and at the 31.2kbps G.729 figure about 32. In practice, leave headroom rather than running the line at capacity.

What internet speed do I need for a VoIP phone system?

Work it out from your peak concurrent calls rather than the number of handsets. Multiply peak calls by your provider's per-call figure, add video meetings and normal use, and check that your upload speed covers it with room to spare.

Why is upload speed important for VoIP?

Every call sends your voice out at the same rate as it brings the other caller's voice in. Business broadband often has much less upload than download capacity, so upload is usually the limit when the line is busy.

Does VoIP need a static IP address?

Hosted VoIP services usually do not. An on-premises phone system connecting to a SIP trunk is more likely to need one. See do I need a static IP for business broadband?

Why do VoIP calls break up when bandwidth looks fine?

Jitter, packet loss, Wi-Fi interference, VPNs or another device saturating the upload are common causes. Microsoft links robotic or cutting-out audio to jitter and packet loss. Prioritising voice with QoS and using wired handsets can help.

Sources

• Cisco: Voice over IP, per-call bandwidth consumption
• Microsoft Learn: Prepare your organisation's network for Teams
• Google Workspace: Voice connectivity requirements
• Virgin Media O2 Business: Cloud Voice FAQs (PDF)
• BT Business: Find out if you can get Cloud Voice

Related guides

• Hosted VoIP for business
• SIP trunking vs hosted VoIP
• Business broadband explained
• 4G backup broadband for business
• Do I need a static IP address?
• Business VoIP phone systems