A 10Gb leased line is a dedicated, uncontended fibre circuit delivering 10,000Mbps symmetric bandwidth for your sole use. In the UK it typically costs roughly £1,200–£3,500 a month on a 3–5 year term, and it suits businesses with heavy cloud workloads, large data transfers or hundreds of concurrent users. For most SMEs, 2Gb or 5Gb is the sensible step first.
How much bandwidth does your business actually use?
Before choosing between 2Gb and 10Gb, measure what you consume rather than guess. Pull a month of usage from your firewall or current router — look at peak throughput (the busiest 5-minute averages), not just the monthly total. Most offices sit well below their headline speed for 95% of the day, then spike at predictable moments — 09:10 on a Monday, or when a 400GB backup kicks off at 2am.
A rough rule of thumb: allow 5–10Mbps per concurrent user for general cloud, Teams and SaaS work, then add headroom for bulk transfers. A 100-person office doing Microsoft 365, Teams calls and some file sync rarely saturates a 1Gb line. The businesses that genuinely need multi-gigabit are those moving large datasets — media, CAD, medical imaging, backup replication between sites, or hosting their own services.
The aim is not to buy the biggest number. The aim is to buy enough committed bandwidth that your busiest hour feels unremarkable. If your current 1Gb line regularly hits 70–80% at peak, it is time to plan the next step up — well before users start complaining about slow uploads.
2Gb, 5Gb, 10Gb and 100Gb leased lines compared
All of these are full leased lines — symmetric, uncontended, with a committed information rate (CIR) and a strict SLA. The difference is the port speed you take and, crucially, the bearer the circuit is delivered over. A bearer is the physical capacity of the fibre tail into your building; your port speed can sit at or below it.
Here is how the common tiers stack up for a typical UK business:
- 2Gb leased line — usually delivered on a 10Gb bearer. Good for mid-sized offices (roughly 50–150 users) with heavy cloud use, VoIP and regular large uploads. A sensible middle ground above standard 1Gb.
- 5Gb leased line — same 10Gb bearer, more port. Suits data-heavy teams, agencies handling large media, or firms consolidating multiple sites' traffic.
- 10Gb leased line — delivered on a 10Gb bearer at full port. For large head offices, data-intensive sectors, or where you host services and need predictable multi-gigabit throughput both ways.
- 100Gb leased line — a specialist, carrier-grade product for data centres, hyperscale connectivity, ISPs and large campuses. Overkill — and over-budget — for all but a handful of enterprises.
What a 10Gb leased line costs in the UK (realistic bands)
Pricing varies by postcode, carrier availability and contract length, so treat these as planning bands rather than quotes. As a rough UK guide, a 10Gb leased line usually runs £1,200–£3,500 per month on a 3–5 year term. The wide spread reflects distance from the nearest fibre point of presence and whether any civil works (digging) are needed.
For context, a 2Gb leased line typically costs £500–£1,200 a month, and a 5Gb line sits somewhere in between at roughly £900–£2,000. Longer contracts lower the monthly figure; shorter terms and difficult installs push it up. A 100Gb leased line is a different category entirely — often several thousand pounds a month plus significant setup.
Watch for two cost drivers that catch businesses out. First, excess construction charges (ECCs) — if a new fibre build is required, the carrier may quote a one-off contribution, sometimes in the thousands. Second, the router and hand-off: 10Gb ports need appropriate optics and firewall capacity, so budget for hardware. We cover the full picture in our leased line cost guide for UK businesses.
When does 10Gb pay off over bonded 1Gb lines?
Some providers suggest bonding or load-balancing several 1Gb lines instead of buying one 10Gb circuit. It can look cheaper on paper, but the two are not equivalent. Bonding spreads traffic across links — a single large transfer or backup stream still can't exceed one line's speed unless the application supports multipath. A true 10Gb line gives any single flow the full headroom.
Bonding does have a place: it can add resilience and aggregate capacity cheaply where multi-gig fibre isn't yet available at a site. But once you need three or four bonded 1Gb lines, the combined rental, extra routers and management overhead often approach the cost of a single higher-capacity circuit — with more to go wrong.
Choose 10Gb when you need guaranteed single-flow throughput, a clean SLA on one circuit, and room to scale by changing a port rather than adding lines. Keep a separate, diverse backup connectivity circuit for resilience — redundancy and raw capacity are different problems, and an SD-WAN overlay can manage both intelligently across sites.
Installation, bearer sizing and future-proofing
The smartest decision many businesses make is ordering the bearer larger than the port they pay for. Take a 10Gb bearer but only light up 2Gb of port today. When you need more, the carrier raises your port speed — often in days, sometimes remotely — with no new fibre, no excavation and no fresh install wait. You pay for 2Gb now and keep a clear upgrade path to 10Gb.
Lead times are the other planning reality. A leased line on existing fibre typically takes 45–90 working days; a new build with civil works can run to 4–6 months. If you're relocating or scaling, start the order early — treat it like a long-lead project, not a quick switch. Our team handles survey, wayleaves and carrier coordination as part of structured IT project delivery.
Also size the kit around the line. A 10Gb circuit behind a firewall that only inspects traffic at 2Gb wastes the investment. Match the router, SFP+ optics and any security appliance to the port speed, and plan the on-site structured data cabling so the hand-off reaches your core switch cleanly.
How to decide: a quick checklist
Run through these points before committing to a tier. If most answers point up, size the port higher — or at least take the larger bearer so you can grow without reinstalling.
- Peak throughput today — are you regularly above 70% of your current line's speed?
- User count and workload — hundreds of concurrent cloud or Teams users, or heavy upload traffic?
- Large transfers — backups, media, CAD or dataset replication measured in hundreds of gigabytes?
- Hosting — do you run services others connect into from outside?
- Growth horizon — will headcount or data double within the contract term?
- Resilience — is a second, diverse line needed regardless of capacity?
Getting the order right for a London site
Availability and price are intensely local. A multi-gig leased line in a well-served postcode near a carrier PoP can be quick and reasonable; the same product a few streets away, across a river or into an older building, may need a new build and a very different quote. Always get a site-specific survey before fixing a budget.
As a London-based provider, we run leased lines, firewalls, Microsoft 365 and support as one accountable service — one number, one invoice. That matters when a circuit lands: someone has to configure the firewall, repoint DNS, and make sure VoIP and cloud traffic behave on day one. See how we handle leased lines in London, or talk to us about sizing before you order.
The aim is not to future-proof forever. The aim is to buy the right port today on a bearer that lets you scale — so your busiest Monday morning stays quiet, and your next upgrade is a config change, not a construction project.