How the comparison works

We divide what you measured by what your package advertises, and put the result into one of three bands. The bands are the same ones the speed test uses — there is one set of thresholds in this product, not one per page.

80% or more — consistent with your package. Protocol overhead, Wi-Fi and normal variation account for the rest.
50% to 80% — below expectation. Real, but the gap on its own does not say where the speed is going.
Under 50% — materially below. Too large to explain by overhead or ordinary variation.

Advertised speed and minimum guaranteed speed are not the same thing

UK broadband is advertised using an average speed that at least half of customers get at peak time. It is a description, not a promise. The figure with contractual force is the minimum guaranteed download speed your provider gave you when you signed up, and under the Ofcom broadband speed code many providers must let you leave without a penalty if they cannot restore it.

One important catch: providers measure that guarantee at the router. A Wi-Fi reading below it does not demonstrate a breach, because your Wi-Fi is not their responsibility. If you intend to raise it, test over a cable first.

What this cannot tell you

It cannot tell you whose fault a shortfall is. A single figure measures the whole path — your device, your Wi-Fi, your router, the line and your provider’s network. A gap proves something in that chain is limiting you; it does not say which link, and we will not pretend otherwise.