What average speed actually means on a broadband advert

The speed on a broadband advert is not a promise about your connection. It is a measured average, taken at a particular time of day, on a particular kind of connection, and it describes the line rather than what your devices receive over WiFi.

That is not a trick, but it does explain the gap most people experience between what they bought and what they get.

Advertised speed means the average download speed at peak time, measured on a wired connection to the provider's own network. Providers must ensure a reasonable proportion of customers actually achieve it. It says nothing about WiFi, and it is usually measured at the router rather than at your device — so a wired test much below the figure is a fault, while a WiFi test below it usually is not.

What the advertised number legally is

Ofcom publishes the rules behind advertised speeds, and runs a postcode checker showing what your line should be capable of. The figure is defined by regulation rather than marketing. It represents the speed a typical customer on that package can expect during peak hours, generally 8pm to 10pm, when contention is highest. Providers must publish it based on actual measurement, and must ensure that a defined share of customers achieve at least that speed.

The practical consequence: if your wired connection consistently delivers well under the advertised figure at peak time, that is not a matter of interpretation — it is a shortfall the provider is expected to fix.

The three numbers that get confused

• Advertised speed — a peak-time average on the provider's network, measured at the router. This is what you actually bought.
• Wired speed at your device — usually slightly below the advertised figure because of overheads and your own hardware. Within about 10% is normal.
• WiFi speed at your device — frequently 30–60% of the wired figure, and worse through walls. This is a property of your home, not a fault on the line.

How to test properly

Most speed complaints are withdrawn after a proper test, because the test was the problem rather than the line.

• Use a cable, not WiFi, for the first test. This isolates the line from your home's radio environment, which is the single most common source of disappointment.
• Test at peak time, in the evening, because that is what the advertised figure describes. A 3am result tells you almost nothing.
• Stop other traffic — cloud backups, updates, other people streaming — before you start.
• Run it three times on different days and keep the results. Providers ask for a pattern, not a single screenshot.
• Use the provider's own speed tester as well as a third-party one; they sometimes disagree, and the provider's is the one they will argue from.

When it is genuinely a fault

A wired connection that consistently delivers substantially below the advertised speed at peak time is a fault. So is a line that drops repeatedly, or one where the speed degrades steadily over days.

Raise it as a fault rather than a complaint, ask for the line to be tested remotely, and request an engineer if the remote test looks clean. If the fault persists unresolved, the complaint route is the same one that applies to billing problems: six weeks to resolve it, then escalation to the dispute resolution scheme.

When the answer is a better router, not a faster line

If the wired speed is close to what you pay for and the WiFi speed is not, buying a faster package will not help. The bottleneck is inside your home. Moving the router off the floor, out of a cupboard, and away from the TV and the kitchen is free and frequently worth more than a speed upgrade.

Beyond that, a mesh system or a single additional access point solves most dead-spot problems for less than the annual cost of a faster tier. Our guide on fixing WiFi dead spots covers the diagnosis in order.