VoIP and Business Broadband: What Connection Do You Actually Need?

Most businesses switching to VoIP ask the same question: "Is our broadband fast enough?"

It's the wrong question. Speed isn't the issue. Stability is.

A 10 Mbps FTTC connection that behaves consistently will handle VoIP better than a 100 Mbps connection that drops packets or spikes in latency every few minutes. Understanding the difference will save you from either overspending on a leased line you don't need, or choosing a connection that makes your calls sound like a bad radio transmission.

Here's what actually matters.

VoIP Uses Very Little Bandwidth

A single VoIP call uses roughly 80–100 kbps of bandwidth — both upload and download — depending on the codec. That's about 0.1 Mbps per active call.

Run ten calls simultaneously and you're using around 1 Mbps of your connection. Most business broadband packages deliver far more than that. Raw speed is almost never the bottleneck.

Where things go wrong is when that bandwidth behaves inconsistently. VoIP sends voice as a continuous stream of tiny data packets. If those packets arrive late, in the wrong order, or not at all, the audio breaks up. Your speed could be excellent on a speed test and you'd still have terrible calls.

The Three Things That Actually Affect Call Quality

Latency is the time it takes a data packet to travel from your phone to the other party and back. It's measured in milliseconds. Below 150 ms is fine. Above 300 ms and you start talking over each other.

Jitter is the variation in that delay. If packets sometimes arrive in 20 ms and sometimes in 180 ms, your phone system struggles to reassemble them into smooth audio. Consistent latency is far more important than low latency.

Packet loss is exactly what it sounds like — packets that never arrive. Even 1–2% packet loss causes audible gaps and robotic-sounding voices. Above 5% and calls become difficult to sustain.

A speed test won't reveal any of these. You need a proper VoIP quality test, which checks your connection under realistic conditions. More on that below.

Which Broadband Connection Type Should You Use?

ADSL

ADSL runs over your existing copper telephone line. It's slower and more susceptible to interference than fibre options. Upload speeds in particular can be very low — sometimes 0.5–1 Mbps — which limits how many simultaneous calls you can handle.

VoIP works on ADSL. Many businesses have used it for years. But the further you are from the telephone exchange, the worse your line quality gets, and that translates directly into jitter and packet loss. Copper lines also pick up electrical interference, especially in older buildings.

The bigger issue: Openreach is switching off the public switched telephone network (PSTN) and ADSL services in 2027. If you're still on ADSL, you'll need to migrate anyway. Better to do it on your terms.

FTTC (Fibre to the Cabinet)

FTTC brings fibre optic cable to the green cabinet on your street, then copper into your premises. It's the most common business broadband type in the UK right now.

For most small and medium businesses, FTTC is perfectly adequate for VoIP. You'll typically get 30–80 Mbps download and 10–20 Mbps upload. Latency is generally low and consistent. Unless you're running a contact centre or your office has 20+ people making calls simultaneously, FTTC handles the job without issue.

The weak point is still the final copper run from the cabinet to your door. If that section of cable is long or in poor condition, you can still see elevated jitter. A good router with QoS settings (see below) usually mitigates this.

FTTP (Fibre to the Premises)

FTTP — sometimes called full fibre — runs fibre all the way into your building. There's no copper in the circuit at all. It's faster, more reliable, and delivers the most consistent performance of any consumer or SME broadband product.

If FTTP is available at your address, it's the best choice for VoIP. Latency is typically very low and extremely stable. Upload speeds are symmetrical or close to it. Jitter is minimal.

Availability has expanded significantly over the past few years, and pricing has become competitive. If you're comparing broadband options for a new office or an upcoming renewal, prioritise FTTP.

Leased Line

A leased line is a dedicated, uncontended connection between your premises and the provider's network. You're not sharing it with anyone. Speeds are fully symmetrical, uptime guarantees are contractual, and latency is rock solid.

Leased lines are expensive — typically £300–£800/month depending on speed and location. They make sense for contact centres, businesses where calls are revenue-critical, or environments running dozens of simultaneous calls at all times.

For a ten-person office making normal business calls, a leased line is overkill. FTTP will do the job for a fraction of the cost.

Quick Reference: Connection Type vs VoIP Suitability

QoS: The Router Setting That Makes a Real Difference

QoS stands for Quality of Service. It's a setting in your router that tells it how to prioritise different types of network traffic.

Without QoS, your router treats a VoIP call and a large file download as equally important. When someone starts pulling down a 2 GB backup at the same time as a client call, the call suffers.

With QoS enabled and configured to prioritise voice traffic, your router ensures VoIP packets always jump the queue. It doesn't increase your bandwidth — it manages it more intelligently.

Most business-grade routers support QoS. It's worth enabling even on FTTC, and it's particularly valuable in offices where multiple people are on calls at once. If you're unsure whether your router supports it, ask your broadband provider or check the router's admin panel for a "traffic priority" or "QoS" section.

Test Your Connection Before You Switch

Before moving your phone system to VoIP, test your existing connection. Don't rely on a standard speed test.

Tools like ping.canopy.tools and Ookla's VoIP test measure latency, jitter, and packet loss specifically. Run the test during business hours — not at midnight — to get a realistic picture of your connection under load.

If you see packet loss above 1% or jitter above 30 ms, investigate before switching. It could be a router configuration issue, a faulty cable between your router and the master socket, or a line fault that your broadband provider can fix.

Our support team at VoIPninjas can help you interpret a connection test result and advise on whether your current setup will work well, or what changes are worth making first. We'd rather tell you about a potential issue upfront than have you go live and experience problems.

Ready to try VoIP on your existing connection? Start your free 14-day trial — no card required, live in 10 working days. Or call us on 0330 043 2388 and we'll talk through whether your broadband is a good fit. Start your free trial → No tie-in, no setup fees. Most businesses are fully live within 10 working days.

Frequently Asked Questions

What broadband speed do I need for VoIP?

Speed is rarely the issue. A single VoIP call uses around 100 kbps. What matters more is consistency — low latency, minimal jitter, and no packet loss. Even a modest FTTC connection will handle VoIP well if it's stable.

Can I use VoIP on ADSL broadband?

Yes, VoIP works on ADSL. Call quality depends heavily on your distance from the exchange and the condition of your copper line. It's worth testing before committing. Bear in mind that ADSL is being switched off in 2027, so a move to fibre is coming regardless.

Is FTTP necessary for VoIP?

No, but it's the best option if it's available at your address. FTTP gives you the most stable, lowest-latency connection of any standard broadband product. Most businesses running VoIP on FTTC have no problems, but FTTP removes almost all broadband-related variables from the equation.

What is jitter and why does it affect VoIP calls?

Jitter is inconsistency in the time it takes data packets to travel across your connection. VoIP relies on a steady stream of packets arriving in sequence. If packets arrive at unpredictable intervals, the audio breaks up or sounds robotic — even if your overall speed is fast. QoS settings on your router can help manage jitter by prioritising voice traffic over other data.