Measure it yourself, in five minutes
Every network publishes a coverage map, and every coverage map is a model of what should reach a place rather than a record of what does. Walls, a hill, a new building or the floor you are on can move it by a wide margin. The useful thing is that your phone already measures the real value, and a handful of apps show it to you properly instead of as four bars that mean almost nothing.
The four numbers worth having
| What to record | Why it matters | Roughly what is good |
|---|---|---|
| Signal strength, in dBm | The bars are a rounded lie; this is the value | Closer to zero is better; -90 is usable, -110 is not |
| Signal quality | A strong but noisy cell still drops calls | Reported separately from strength; check both |
| Which band and technology | Low bands travel through walls, high bands do not | Note whichever your phone actually latches |
| Download and upload speed | The figure the contract is sold on | Compare against what was promised, at peak time |
| Latency and jitter | What decides whether calls sound bad | Consistency matters more than the average |
| Where in the building | The variation indoors is often larger than between streets | Test the rooms you will use, not the doorway |
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The apps
Speedtest by Ookla: the reference for throughput, and the result everyone else recognises when you complain to a provider.
Speed plus a coverage view built from real readings rather than a propagation model, which is exactly the difference that matters here.
Network Cell Info Lite: strength, band, cell identity and a log over time. The most informative of the free options for mobile signal.
Netmonitor: shows which cell you are attached to and lets you log readings as you move, so you can map a flat room by room.
Focused on band and technology detail. Useful for working out whether that one usable corner is on a different band from the rest of the house.
Network Signal Info: a clear single screen of mobile and WiFi strength, with a widget, which is the fastest way to take a reading while walking around.
PingTools: ping, traceroute, DNS and a LAN scan in about 9 MB. The app for proving where a problem actually sits.
Network Analyzer: the same class of tool, well rated, with a clean interface for checking what else is on the network.
Fing: identifies every device on the WiFi, which is how you discover the slow evening is a neighbour on your network rather than the line.
WiFiman: throughput plus a tidy view of channels and nearby networks. One of the better looking and better behaved WiFi tools.
WiFi Analyzer, open source and about 3 MB. Shows channel overlap plainly, which is the single most common fixable WiFi problem in a block of flats.
The most popular of the analyzers with a friendlier presentation of the same channel and strength data.
Another WiFi analyzer with a good signal-over-time graph, which is what you want while walking from room to room.
The original, around 1 MB, still functional and still the smallest thing that will draw a channel graph. Its rating reflects its age rather than its accuracy.
More detailed than most, including per-band reporting and exportable results. Fiddly, and the right tool if you are building a case.
Network Monitor Mini: live throughput in the status bar. Not a diagnostic, and the quickest way to see whether anything is moving at all.
A five minute survey of a flat
- Note the number in each room, standing still Strength readings swing while you walk. Stop, wait a few seconds, then read.
- Include the rooms you will actually use The hallway by the window is always fine. The bedroom at the back is the one that decides.
- Check whether it falls back to an older technology A phone that drops from 5G or 4G to something older indoors will make calls but struggle with data.
- Run two speed tests, morning and evening One number is an anecdote. The gap between the two is the useful information.
- Test with the other network too, if you can A second SIM, or a friend's phone on another provider, turns a complaint into a comparison.
- Write it down before you forget which room was which Every one of these apps can log or export. Six remembered numbers become three by the next day.
What to do with a poor reading
If the signal is weak but present, WiFi calling usually solves voice entirely, and it is a setting rather than a purchase. If data is the problem and the broadband is fine, that is the same answer. Signal boosters are a different matter: in many countries operating one without the network's permission is illegal, so check before buying anything that claims to amplify a mobile signal.
If the reading is poor on every network in every room, that is worth knowing before signing a tenancy agreement or a two year contract, which is the entire reason to spend five minutes on this.
Read the dBm, not the bars. Test the rooms you will use, at the hour everyone is home, and write the numbers down.
Frequently asked questions
Why does the app show a different signal from the bars?
Bars are a manufacturer's rounding of the same underlying value, and different phones round differently. The dBm figure is the measurement; the bars are a summary of it.
Is there any risk in installing network tools?
Judge them on permissions. Signal readings need location, which is legitimate here. Anything in this category asking for contacts, messages or accessibility access is asking for something it does not need.
Can an app improve my signal?
No. Nothing installed on the phone can increase the radio power or move the cell tower, whatever the name promises. What helps is WiFi calling, a window, and occasionally a different network.
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