It is one of the most common complaints in any home or small office: the plan says 100 Mbps, the speed test says 30, and it is not obvious who is at fault. The good news is that this is a solvable problem with a fixed order of checks. Work through them in order and you will know within ten minutes whether the issue is your wifi, your router, your neighbours, or your provider — and you will have the evidence to prove it.
First, understand what you were actually sold
Most consumer broadband is sold as an "up to" speed, not a guaranteed one. That phrase is doing a lot of work. It means the provider has committed to a maximum under ideal conditions, not a floor. On a shared line — cable, or fibre-to-the-node — the capacity is divided among everyone connected to the same segment, so the speed you get at 9pm is not the speed you get at 11am.
There is also a units trap that accounts for a surprising share of complaints. Plans are sold in megabits per second (Mbps). Downloads in your browser are usually shown in megabytes per second (MB/s). There are eight bits in a byte, so a perfectly healthy 100 Mbps connection downloads a file at about 12.5 MB/s. If that is the number that worried you, nothing is wrong.
The one test that splits the problem in two
Almost every slow-internet case is either "the line is slow" or "the last few metres are slow". One test separates them.
Plug a laptop directly into the router with an Ethernet cable and run a speed test. Then unplug, connect to wifi from the same spot, and run it again.
- Wired is fast, wifi is slow — your line is fine. The problem is wifi, and the rest of this article's wifi section applies.
- Both are slow — the problem is upstream: your router, your provider, or congestion. Skip to the line section.
This single comparison saves most people a pointless support call, and it is the first thing a competent support agent will ask you to do anyway.
If wifi is the bottleneck
Wifi is radio, and radio degrades with distance and obstacles. A few things matter far more than people expect:
- Distance and walls. Every wall costs you throughput, and concrete or brick costs a lot. Two rooms away through two walls can easily halve a connection.
- The band you are on. The 2.4 GHz band travels further but is slower and heavily congested — it shares space with microwaves, cordless phones and every neighbour's network. The 5 GHz band is much faster over short distances. Many older devices only support 2.4 GHz, which quietly caps them.
- The router's own ceiling. A router supplied five years ago may not be able to forward more than a few hundred Mbps regardless of what arrives at it. If you upgraded your plan but kept the old router, this is a very common cause.
- Where the router physically sits. Inside a cabinet, behind a TV, or on the floor in a corner are all bad. Central, elevated and in the open is measurably better.
Test in each room and write the numbers down. A map of your home's dead spots is worth more than any single reading, and it tells you whether you need a mesh node or just a better router position.
If the line itself is slow
If a wired test is also slow, work through these:
- Check what else is running. A cloud backup, a game update, or someone streaming 4K in another room will consume the connection. Pause everything and retest — this alone explains a lot of "random" slowdowns.
- Test at two different times. Run one test mid-morning and one at 9pm. If the morning test hits your plan speed and the evening test collapses, you have peak-hour congestion on a shared line. That is a real problem and a legitimate thing to raise, but it is not a fault on your connection.
- Restart the router properly. Power it off for thirty seconds, not just a quick reboot. Routers accumulate state and genuinely do degrade over long uptimes.
- Compare against your provider's own test. Their test usually connects to a server inside their network, so it measures the link to their nearest node rather than the wider internet. If their test is fast and an independent test is slow, the constraint is beyond their network or at capacity. If both are slow, the fault is likely on your line.
What to collect before you complain
Providers respond to patterns, not to a single screenshot. Before you open a ticket, gather:
- At least five test results, taken across different days, including two during evening peak.
- At least one wired result, so wifi cannot be blamed.
- The times of each test, and the plan speed you are contracted for.
That set of evidence changes the conversation completely. Instead of "my internet is slow", you are saying "my 100 Mbps line delivers 92 Mbps wired at 11am and 24 Mbps wired at 9pm across four evenings" — which is a specific, checkable claim that support has to engage with.
A realistic expectation
A healthy connection typically delivers 80-95% of its rated speed on a wired test at a quiet hour. Over wifi, on a good router, in the same room, 60-80% is normal. Further away, less. If you are inside those bands, your connection is working as intended, and the fix — if you want more — is better wifi coverage rather than a bigger plan.
If you are far outside them on a wired test at a quiet hour, you have a genuine case. Run the test, save the results, and take the pattern to your provider.
