What internet speed is required for VoIP?

VoIP itself is surprisingly light on bandwidth per call, roughly 100kbps for a standard call, though the real planning number is total concurrent usage across your whole office, not per-extension.

The Per-Call Numbers

A typical VoIP call using a standard codec uses approximately 85 to 100kbps in each direction (upload and download combined, roughly). Higher-quality HD voice codecs use somewhat more, in the range of 150 to 200kbps, while more compressed codecs designed for constrained connections can use less, though generally at some quality trade-off.

Working Out Your Actual Requirement

The right way to size this is by concurrent calls, not total extensions. Most offices don't have every extension on a call simultaneously, a reasonable planning assumption is that 20 to 30% of extensions might be actively on calls at peak times. For a 50-extension office, that's roughly 10 to 15 concurrent calls, requiring approximately 1 to 1.5Mbps just for voice, comfortably achievable on almost any modern business connection.

Why Upload Speed Matters as Much as Download

Voice is a real-time, two-way conversation, so your upload speed (often the more constrained side on asymmetric connections) needs to comfortably handle your concurrent call volume just as much as download. This is one reason fibre, with its typically symmetrical speeds, tends to deliver more consistent VoIP performance than connections with heavily asymmetric upload/download ratios.

Latency Matters More Than Raw Speed

Beyond raw bandwidth, latency (the delay for data to travel to its destination and back) has an outsized impact on how a call actually feels. High latency causes the awkward "talking over each other" experience common on poor international calls, even when bandwidth itself is adequate. Fibre generally offers the lowest, most consistent latency; satellite-based connections, by contrast, have inherently higher latency due to the physical distance signals travel, making them a poor fit for VoIP specifically even when bandwidth numbers look fine on paper.

Don't Forget Everything Else Sharing the Connection

The voice bandwidth calculation above assumes voice has the connection to itself. In reality, that same connection is also carrying email, cloud application traffic, video calls, and file transfers. The practical sizing recommendation is to calculate your voice requirement, then add meaningful headroom, at minimum double the voice-only figure, for everything else running concurrently, and more if the business also runs video conferencing or heavy cloud usage.

A Practical Example

A 30-person office running VoIP, with roughly 8 to 10 concurrent calls at peak plus normal email, browsing, and occasional video calls, would comfortably run on a 20 to 30Mbps connection with proper QoS configuration, well within range of a standard business fibre package.

Our Approach

Rather than quoting a generic bandwidth number, we size connectivity requirements based on your actual extension count, expected concurrency, and whether video or heavy cloud usage is also part of the picture, then configure QoS to make sure voice traffic is protected regardless of what else is happening on the connection.