Bandwidth Calculator — How Many Mbps Do You Actually Need?

How the Calculation Works

The calculator multiplies three things together:

1. Per-user bandwidth, the sum of every application you ticked. A user on email, web and Teams needs roughly 5.1 Mbps.
2. Concurrency, the share of your users actually generating traffic at the same moment. In a normal office this is around 50%, not 100%. Sizing for 100% concurrency is the single most common way people overpay for a circuit.
3. Headroom, the recommended figure adds 25% on top of the base requirement, and the peak figure adds 50%. Networks that run permanently at 100% utilisation feel slow long before they saturate, because queuing delay rises sharply as you approach capacity.

So 10 users at 50% concurrency, each needing 5.1 Mbps, gives a base of 25.5 Mbps and a recommendation of 32 Mbps.

Bandwidth Requirements by Use Case

Typical Bandwidth per Application

Do Not Forget Upload Bandwidth

Most consumer broadband is asymmetric, you might get 500 Mbps down but only 20 Mbps up. Video calls, cloud backup and remote desktop all consume upload as heavily as download. An office of 20 people on video calls needs roughly 70 Mbps of upload, which many “fast” consumer plans cannot deliver. If your users complain that meetings freeze while downloads run fine, upload saturation is almost always the reason.

When Bandwidth Is Not the Problem

Buying more bandwidth does not fix every slow network. Check these before upgrading the circuit:

• Latency and jitter. A voice call needs under 150 ms of latency and under 30 ms of jitter. More bandwidth does not reduce either.
• Packet loss. Even 1% loss badly degrades TCP throughput. Find the cause rather than adding capacity.
• Wi-Fi, not WAN. If the bottleneck is a congested access point or a weak signal, the internet circuit is irrelevant. Check actual throughput at the client.
• Duplex mismatch or a bad cable. A single port negotiating at 100 Mbps half-duplex will throttle everything behind it.
• No QoS. Without prioritisation, one large upload will starve every voice call on the link.

Frequently Asked Questions

Is 100 Mbps enough for an office of 20 people?

For light use, email, web browsing and the occasional call, yes. If the team runs video conferencing, cloud storage sync and large file transfers, plan for 200 to 500 Mbps. Read our breakdown of what 100 Mbps actually gets you.

What is the difference between bandwidth and speed?

Bandwidth is the maximum capacity of the link, measured in Mbps or Gbps. Speed is how fast data actually moves in practice, which latency, packet loss and congestion all reduce. A 1 Gbps link with 5% packet loss will feel slower than a clean 100 Mbps one. See bandwidth in networking for the full explanation.

Why does the calculator use a concurrency percentage?

Because sizing for every user at once is how organisations end up paying for three times the circuit they need. In a typical office roughly half the users are generating traffic at any given moment. Use 70% for a call-centre style environment and 100% only when you genuinely know every seat is active simultaneously.

Should I size for the minimum or the recommended figure?

Use the recommended figure. The minimum is what the network needs to function at all; at that level any burst causes visible slowdown. The peak figure is worth buying if you expect growth within the contract term, since circuit upgrades usually mean a new contract.

Does the number of devices matter, or just users?

Users, mostly. One person with a laptop, a phone and a tablet still generates roughly one person’s worth of active traffic. Count devices separately only when they run independently, security cameras, digital signage and IoT sensors all consume bandwidth with no user attached.

Related Tools and Guides

Test what you are actually getting with our WiFi speed test, plan your address space with the subnet calculator and VLAN calculator, or read what throughput means and why internet speed fluctuates. See all our free networking tools.