What Internet Speed Do You Need for VoIP? Bandwidth, Latency and Jitter Explained (UK 2026)

Quick answer

VoIP needs very little bandwidth: about 100 kbps in each direction per concurrent call, so ten simultaneous calls fit comfortably inside 1 Mbps. Almost any UK business broadband has that many times over. What VoIP actually needs is a stable connection: latency (delay) under about 150 ms, jitter (variation in delay) under about 30 ms, and packet loss under 1 per cent. Those three, not the headline speed, decide whether calls sound clear or robotic. A full fibre (FTTP) or SoGEA line with a decent router that prioritises voice traffic (QoS) carries hosted telephony well; an old copper ADSL line shared with a busy office, or a congested Wi-Fi network, is where problems start. Every hosted telephony quote should include a line test that measures all three.

We test every line before quoting, and the results are the single best predictor of whether a customer will be happy. This guide explains the numbers, how to test them yourself and what to do if they are poor. If you want us to run the test, get a no-obligation quote.

How much bandwidth a VoIP call uses

A hosted telephony call is encoded by a codec. The common ones:

Call it 100 kbps each way per call to be safe. Ten people on the phone at once is 1 Mbps up and 1 Mbps down. A 40 Mbps SoGEA line or a 100 Mbps full fibre line has room for hundreds of calls; the only time bandwidth itself matters is on a very slow or very congested line, or when upload is tiny (old ADSL uploads of under 1 Mbps shared with cloud backups and video calls).

Why latency, jitter and packet loss matter more

Voice is real time. A web page arriving half a second late is fine; half a second of delay in a conversation makes people talk over each other.

• Latency is the one-way delay. Under about 150 ms is unnoticeable; over 250 ms people start interrupting each other. UK fibre lines are typically 10 to 30 ms.
• Jitter is variation in that delay. Packets arriving unevenly have to be buffered, and if the buffer runs out the audio breaks up. Under about 30 ms is the target. Jitter is usually caused by congestion - somebody's cloud backup or video call saturating the line - or by Wi-Fi.
• Packet loss is packets that never arrive. Voice cannot wait for a retransmission, so lost packets become dropouts. Under 1 per cent is acceptable; over 2 or 3 per cent is audible.

A connection can have plenty of bandwidth and still be poor for voice if it is congested or unstable. That is why "we have 100 Mbps fibre" and "the calls sound terrible" are not contradictory, and why the fix is usually the router or the network, not more speed.

How to test your connection for VoIP

A basic speed test tells you bandwidth and usually latency; it does not tell you jitter or packet loss under load, which is what matters. A proper VoIP line test runs for several minutes, simulates concurrent calls and measures all three. Any reputable hosted telephony provider will do this before quoting; we do it as standard. If you want a first look yourself, run a test during your busiest hour, not at 8 a.m., and repeat it over a couple of days. A single good result means little.

Counting concurrent calls

Size the connection on simultaneous calls, not headcount. A rough guide for an office: one concurrent call per five to eight users, more for sales or support teams that live on the phone, fewer for workshops and warehouses. A twenty-person accountancy practice might peak at four or five calls at once; a ten-seat support desk might peak at ten. Your current phone system or bill can often tell you the real peak.

The router and network: where most problems live

The single most effective thing you can do for call quality is a business-grade router with Quality of Service (QoS) configured to prioritise voice traffic. When someone starts a large upload, QoS makes sure the voice packets go first. Consumer routers supplied with broadband rarely do this well. Beyond the router:

• Wire the desk phones. Ethernet, ideally on a separate VLAN for voice. Wi-Fi adds jitter and contention.
• If phones must be wireless, give voice its own Wi-Fi network and make sure the access points are business grade and not overloaded.
• Power over Ethernet (PoE) switches power desk phones without adapters and keep the installation tidy.
• Check what else is on the line. Cloud backups, CCTV uploads and video meetings are the usual jitter culprits; schedule or shape them.
• Keep firmware current on the router and handsets.

Our guide to common VoIP problems and their fixes walks through the symptoms in detail.

Which UK connections carry VoIP well

If your business is on copper broadband that shares a phone line, the PSTN switch-off will force a change anyway; moving to SoGEA or FTTP first, then to hosted telephony, is the right order. Our connectivity guides cover business broadband, full fibre and leased lines.

What to do if your line is poor

First, find out why. Congestion and consumer routers are the common causes and are cheap to fix. A genuinely poor line - high latency or loss even when idle - needs a different product: an upgrade to FTTP where available, or a leased line for a larger office. In the meantime, or as permanent belt-and-braces, a 4G or 5G failover keeps calls going when the main line is bad, and the hosted platform can divert to mobiles automatically. Do not move to VoIP on a line you know is poor and hope; fix the connectivity first.

Remote and home workers

The same rules apply at home, with less control. Most UK home broadband carries a single VoIP call easily; problems come from busy household Wi-Fi and consumer routers. Practical advice for home workers: use the mobile app on a wired or strong Wi-Fi connection, use a headset, and fall back to the app on 4G if the home connection misbehaves. Our guide to hosted telephony for remote and hybrid teams covers the set-up.

The bottom line

VoIP needs about 100 kbps per concurrent call and almost any business connection has that many times over. Call quality is decided by latency, jitter and packet loss, which come from congestion, Wi-Fi and consumer routers far more often than from the line itself. Test properly during a busy hour, count concurrent calls rather than staff, wire the phones, and use a router that prioritises voice. Do that and hosted telephony sounds better than the landline it replaced.

We run the line test as part of every quote and tell you plainly if the connection needs work first: get a no-obligation quote or call 0333 006 9399. Our hosted telephony service page explains what the assessment covers.

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