When Wi-Fi feels slow, the most common guess is that the signal is weak. Sometimes that's right, often it isn't.
An analyzer app turns that guess into a number. The trouble is that the numbers it shows are rarely explained, and without understanding them, the app is no more useful than the ordinary signal bars.
Reading dBm values
The main figure shown is negative, for example -52 dBm. This is not a bad score.
The closer to zero, the stronger the signal. And the scale isn't linear: every drop of 3 dBm means half the power. The gap between -50 and -80 isn't small, it's roughly a thousandth of the strength.
| Value | Condition | Good enough for |
|---|---|---|
| -30 to -50 | Very strong | Anything, including 4K |
| -50 to -60 | Strong | Smooth video calls |
| -60 to -70 | Adequate | General use |
| -70 to -80 | Weak | Messaging and browsing only |
| Below -80 | Very weak | Frequent drops |
If the reading where you normally work is better than -60 but the internet is still slow, the problem isn't signal. Point your investigation elsewhere, the guide to full signal but slow internet explains why.
Finding an uncrowded channel
This is the most valuable use of an app like this, especially in dense housing.
On the 2.4 GHz band, the channels overlap each other. Only channels 1, 6, and 11 are spaced far enough apart not to interfere. Using channel 3 means disrupting channels 1 and 6 at once, while being disrupted by both.
Open the graph view in the app. The horizontal axis is channels, and each network is drawn as an arc. What you're looking for: among channels 1, 6, and 11, which has the fewest and lowest arcs.
Note that networks with weak signals still interfere. A neighbour's Wi-Fi reading just -80 dBm still makes your device wait its turn.
On 5 GHz the problem is far milder. There are more channels and they don't overlap. If your devices support it, moving to 5 GHz is often more effective than fiddling with 2.4 GHz channels. The comparison is in the guide to Wi-Fi frequency bands.
Mapping the weak spots at home
A simple way to find exactly where your coverage breaks down:
- Open the app and let it display signal strength.
- Walk slowly through every room, noting the numbers.
- Pause a few seconds at each spot, the reading needs time to settle.
- Mark them on a rough floor plan, especially anywhere below -70 dBm.
The results are often surprising. Weak spots are rarely at the point furthest from the router; more often they're behind one particular wall, a concrete staircase, or a large cabinet.
If the weak spots cluster in one area, moving the router may be enough, covered in the guide to router placement. If they're scattered, you need an extra access point, and this map shows where it should go.
Without installing anything
Windows already provides what you need. Open Command Prompt and run
netsh wlan show interfaces to see the signal strength of the connected network, the
channel in use, and the link speed.
On macOS, hold the Option key and click the Wi-Fi icon in the menu bar. RSSI, channel, and channel width appear immediately with nothing installed.
For Android, analyzer apps are plentiful and mostly free. For iOS, capability is limited because the system doesn't let apps scan surrounding networks.
Things to keep in mind
Apps like this make it easy to fixate on numbers. Two reminders:
- A strong signal is no guarantee of speed. It only means the device and router hear each other clearly. Capacity, channel congestion, and your subscription speed are separate matters.
- Fluctuating numbers are normal. A few dBm up and down happens constantly. What matters is the pattern, not a single reading.
If the signal numbers look fine but the connection still misbehaves, the next sequence of checks is in the guide to fixing slow Wi-Fi and the guide to Wi-Fi that keeps disconnecting.
Frequently asked questions
Why is the signal value negative?
Because it's measured in dBm, a unit comparing power against one milliwatt. Wi-Fi signals are always far below that figure, so the result is negative. The thing to remember: closer to zero is stronger, so -45 is far better than -75.
What dBm value is still acceptable?
Above -60 dBm is excellent for anything, including video calls. Between -60 and -70 is still comfortable for general use. Below -75 it starts to stutter, and below -85 it's practically unusable.
Why are only channels 1, 6, and 11 recommended on 2.4 GHz?
Because each channel uses a bandwidth that overlaps its neighbours. Only those three are spaced far enough apart not to collide. Using channel 3 or 9 means interfering with two channels at once.
Are these apps available for iPhone?
Only in limited form. iOS doesn't let apps read information about surrounding networks the way Android does. For a full scan, use an Android phone or a laptop; on Windows the built-in commands are perfectly adequate.
