The package says 900 Mbit/s. The laptop on the sofa says 280, a shade under a third of it, which makes the advertised number more than three times the one you are living with. Neither figure is a lie, and the distance between them is where most broadband complaints begin and end, because almost nobody measures in a way that would stand up to a provider.
Four bottlenecks, one after the other
The advertised figure describes what the line can carry at the point it enters the house. Everything after that subtracts.
The first cut is shared capacity. A full fibre branch serves dozens of homes, so the headline speed is genuinely there at ten in the morning and is quietly flattened for everyone at nine in the evening. The second is Wi-Fi, and it is by far the biggest single loss: a few metres, a wall and a crowded channel routinely halve what the router is being fed.
The third is your own kit. A network port limited to 100 Mbit/s, a tired patch cable or a budget phone with an old radio in it will cap the result whatever the line is doing. A gigabit Ethernet port tops out at around 940 Mbit/s in real traffic, so a gigabit package can never test at a gigabit on it. The fourth is the far end, because a speed test or a streaming platform imposes its own ceiling and you end up measuring that server rather than your connection.
One rarer cause is worth knowing about. A poorly terminated connector, a fibre pinched in its conduit or a worn optical socket produces a shortfall at every hour of the day, and it is the provider's engineer who puts it right.
Measure it properly, or the complaint goes nowhere
- Plug the computer straight into the router with a cable, cat 5e as a minimum. Anything measured over Wi-Fi tests your home network, not the line your provider sold you.
- Stop everything else first. A console updating itself in another room or a cloud backup running quietly is enough to spoil the figure.
- Test repeatedly, at different hours. Ten in the morning and nine at night tell two different stories, and it is the range you want, not your best single result.
- Compare against the contract rather than the advert, because those are two different numbers and only one of them means anything.
Screenshot every run with the time visible: a pattern held over a fortnight turns an irritation into a case. Our guide to running a broadband speed test that actually means something has the detail.
The three speed figures in your paperwork are not interchangeable
Only the guaranteed minimum speed carries a remedy, and it is the number nobody remembers being given. It is set out at the point of sale under Ofcom's voluntary code on broadband speeds, which the large providers have signed.
If your speed drops below that floor, tell the provider in writing and keep the reference number. They get one calendar month to put it right. If the speed is still under the floor at the end of it, you can leave without paying an exit fee, and that covers any phone or television service bundled into the same contract.
If it stalls, you can take it to your provider's alternative dispute resolution scheme, free of charge, once eight weeks have passed or you have a deadlock letter.
Speed you can get back tonight, for nothing
- Run a cable to the devices that eat the most, typically the television, the games console and the desk you work from. Every one you take off Wi-Fi leaves more of it for the rest.
- Push the demanding devices onto the 5 GHz band, since phones and laptops drop back to 2.4 GHz on their own as soon as the signal weakens and stay there.
- Get the router out of the cupboard. High, clear, roughly central, not behind the television and not at the end of a corridor.
- Replace an ageing extender with a mesh system, or with the provider's own kit. A cheap extender in the wrong place halves the speed it passes on instead of extending anything.
Work out what you actually need before you pay for more
A 4K stream needs somewhere around 25 Mbit/s, a video call about five. Online gaming barely registers on throughput and cares almost entirely about low, stable latency. Add up a normal evening and the total is usually modest.
A household of four rarely troubles 300 Mbit/s of real, measured speed. What does make a daily difference is the upload, which carries video calls and cloud backups, and the quality of the router itself. Check both before you switch broadband provider in search of a bigger number.
Worth knowing: falling short of the advertised speed is not in itself a breach of anything. The shortfall has to be measured against the guaranteed minimum, over a wired connection, and repeatedly.