How much leased line bandwidth does my business need, 100Mbps to 10Gbps?

Picking leased line capacity is one of the few broadband decisions where guessing is expensive in both directions. Buy too little and the connection chokes the moment everyone is online at once. Buy far too much and you're paying every month for headroom you never touch. The good news is that sizing a leased line isn't guesswork once you look at how the connection is actually used rather than how many desks you have.

This guide is about capacity sizing only: how to choose between 100Mbps, 500Mbps, 1Gbps and 10Gbps for a leased line. It doesn't cover whether a leased line is the right product for you in the first place, that's a separate decision. If you already know you want the dedicated, symmetric, contended-by-nobody connection a leased line gives you, this is the page that helps you pick the size.

The right leased line bandwidth depends less on company size alone and more on how the connection is used. A 100Mbps line can be enough for a small office, while cloud-heavy, multi-user, or multi-site businesses often need 1Gbps or more. 10Gbps is usually for serious data volume, resilience, or growth.

How much leased line bandwidth does a small business need?

For most small businesses, the honest answer is "less than you might fear, but think about uploads". A small office of roughly 5 to 15 people doing email, web browsing, a few cloud apps and the occasional video call typically runs comfortably on 100Mbps. Because a leased line is symmetric, that 100Mbps applies to uploads as well as downloads, which is already a large step up from a typical part-copper or shared fibre line where upload is the weak point.

What changes the picture for a small business isn't the headcount on its own, it's the intensity of use. A five-person studio that pushes large video files to the cloud all day will lean on the line harder than a thirty-person office doing mostly text and spreadsheets. So the first question isn't "how many staff?", it's "what do they all do at the same time, especially when uploading?". Hold that thought, because it runs through every tier below.

What can 100Mbps, 500Mbps, 1Gbps, and 10Gbps actually handle?

The table below maps common business shapes to a recommended tier. Treat the figures as a starting point rather than a hard rule: two businesses with the same headcount can need very different capacity depending on how data-heavy their day looks. The language is deliberately cautious ("roughly", "typically") because real workloads vary.

Notice that the bands overlap on purpose. A growing office could land anywhere between 500Mbps and 1Gbps, and where it lands depends almost entirely on how much it uploads and how much of the day runs through the cloud. The next section unpacks the factors that move you up or down within a band.

How do users, cloud apps, voice, and uploads change the requirement?

Four things tend to decide where a business really sits, and they matter far more than raw headcount.

• Concurrent users. What counts isn't how many people are employed, it's how many are generating traffic at the same moment. Twenty people who all sync large files at 9am hit the line harder than fifty who trickle through email across the day.
• Cloud apps. When the business runs through cloud platforms (file storage, hosted software, remote desktops, accounting and CRM all living off-site) every action becomes network traffic. A cloud-first office of the same size as an on-premise one needs noticeably more capacity.
• Voice. Hosted phone systems are light per call, but they're sensitive to congestion. The bandwidth a busy office of calls uses is modest, the real requirement is that voice has clean, consistent headroom so calls don't break up when the rest of the line is busy.
• Uploads. This is the one businesses underestimate most. A leased line is symmetric, so upload capacity is as valuable as download. Constant backups, sending large files to clients, video uploads and pushing data to the cloud all live on the upload side, and they're what quietly push a business into the next tier. Our guide on upload speed for video calls digs into why upload, not download, is usually the limiting factor.

Add these up rather than looking at any one in isolation. A small team that is cloud-first, on calls all day and constantly uploading can need as much capacity as a much larger team doing lighter work.

When does 1Gbps make more sense than 100Mbps?

The jump from 100Mbps to 1Gbps is the most common upgrade question, and it's rarely about reaching a magic number of staff. It's about sustained, simultaneous load. A 100Mbps line is fine until the moments when everyone is busy at once start to feel slow: backups crawling, video calls wobbling when someone uploads a big file, cloud apps lagging mid-morning. Those symptoms are the line telling you the workload has outgrown the tier.

In practice, 500Mbps to 1Gbps starts to make sense once you've roughly 15 to 50 people leaning hard on cloud platforms and video, you run more than one site sharing data, or your day involves regular large uploads that a 100Mbps line has to queue. The deciding factor is almost always how much you push outbound and how much of that happens at the same time. If your work is bursty and upload-heavy, step up before you feel the pain rather than after. Most genuinely cloud-dependent offices end up on capacity in this band and are glad of the headroom.

Who really needs a 10Gbps leased line?

10Gbps is a serious step, and most businesses never need it. It's for organisations where the connection itself is critical infrastructure rather than office plumbing: data centres, large multi-site operations, media and post-production houses moving enormous files, software firms shifting big datasets, and anywhere with sustained, very high data volume. For these, the line isn't a convenience, it's part of how the business runs.

The other reason businesses choose 10Gbps is headroom and resilience. Somewhere that simply cannot afford to run close to capacity, or that needs deep margin so a spike never becomes an outage, will size up deliberately. If that's you, it's worth pairing the capacity decision with a clear SLA so the resilience you're paying for is backed by guaranteed availability and fix times, not just a big number on the line. For a normal office, though, 10Gbps is far more than the workload calls for, and the money is better spent elsewhere.

Should I size for today, or for growth over the contract term?

The sensible middle ground is to size for today plus the growth you can actually see coming. A leased line is typically taken on a multi-year term, so it's worth thinking about where you'll realistically be in 12 to 24 months, not just where you are on install day. Headcount plans, a move to more cloud platforms, a second site: all of these change the answer.

That said, wholesale overbuying isn't the answer either. A leased line is built to scale, and stepping the bandwidth up later is often straightforward, frequently without re-running any cabling. So the balanced approach is to choose enough capacity to cover today and your known near-term growth, leave a little headroom for comfort, then upgrade when the workload genuinely calls for it rather than paying years ahead for capacity you might never use.

If you're not sure where your business lands, the quickest route is to talk it through with someone who sizes these connections every week. You can get a leased line quote and we'll help you match the tier to how you actually work. Home workers and very small setups should look at home office broadband first, since a full leased line is usually more than a single home worker needs.

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