Use a capable wired device for a baseline, record both download and upload, and repeat under comparable conditions. Compare the result with the personalised service estimate and contract terms, not just the largest number in an advert.
Once you know the speed you need, use our London broadband overview to compare local coverage and networks.
Understand what is being measured
Download measures incoming transfer rate and upload measures outgoing transfer rate. Latency describes delay. Some tests also show delay while the connection is busy, which can help explain why calls or games feel worse during a large transfer.
A high download result does not prove that every website will respond quickly. Each remote service has its own path and limits. Treat the test as one piece of evidence alongside the activity that is actually failing.
Create a repeatable baseline
Connect a suitable computer directly to the router with Ethernet where possible. Pause large transfers on your own devices and note whether anyone else is using the connection. Choose a reputable test and record the server or test location when shown.
Check the computer's wired link rate first. An older adapter or a link negotiating at 100 Mbps can limit the result before traffic reaches the broadband service. A very fast subscription also needs suitable ports, adapters and device capability to be tested fully.
Compare the same conditions
Take a small set of readings at different relevant times, including when you usually notice trouble. Keep the device, connection method and test service consistent. Avoid running several speed tests simultaneously because they compete with one another.
Next compare Wi-Fi nearby and in the difficult room. If the wired baseline is sound while the room is poor, investigate the indoor connection. If every capable wired test is poor, you have more useful evidence for the provider.
| Pattern | Useful next check |
|---|---|
| Good wired, poor distant Wi-Fi | Wireless placement, access points and client capability |
| Poor wired and wireless | Quoted speed, router link, background traffic and provider support |
| Good downloads, poor uploads | Upload tier and concurrent backups |
| Good idle ping, poor busy experience | Latency under load and competing transfers |
Compare with the right promise
Ofcom explains that advertised average speeds reflect what at least half of customers achieve at the busy time, rather than a guarantee for every address. The personalised estimate and any minimum-speed commitment are therefore important documents.
Ofcom's voluntary speeds-code protections apply to participating providers. If the provider's network is responsible and the qualifying problem remains unresolved within the applicable process, rights to exit may apply. Check the current code and your own contract rather than assuming every provider has identical terms.
Report the pattern clearly
Send the support team the times, connection method, device details and the recurring symptom. Explain whether you tested directly at the router and whether the problem affects more than one service.
Ask for a case reference and the next diagnostic step. Keep the evidence proportionate: a short clear set of comparable results is usually more actionable than dozens of mixed tests with no record of how they were taken.
Your questions, answered.
Why is my result lower than the package's headline speed?
Possible limits include protocol overhead, the actual service tier, the device, its adapter, Wi-Fi, other traffic and the test server. Compare a controlled wired result with the provider's personalised terms.
Is this site's speed planner measuring my broadband?
No. It is an educational calculator. Use a real connection test when you want to measure your current service.
Sources & further reading
Official information behind this guide. Links checked 29 October 2026; individual datasets retain their stated reference dates.